Assuming you're asking in good faith:
1) My idea of "good/well designed" is if a Job isn't clunky and counterintuitive (Old PLD was clunky and counterintuitive, such as needing to drop Atonements), is understandable to general player bases (a more complex Job can still be well designed, but will be more niche, and it requires a lot to make sure the complexity is good and not clunk), works well within the combat system (e.g. doesn't work like a stationary turret in a game where encounters require lots of movement, or if it does, has tools to account for this), can complete the requirements of the role (agro and surviving hits, healing, and damage dealing, for Tanks/Healers/DPSers, respectively). The abilities should be internally consistent and flow between each other smoothly (no weird stutter step "rotations" or designed/required clipping and so on), and ideally the abilities should have interactions with each other within the kit. OPTIONALLY but generally a good idea, the abilities fit within the class lore and fantasy.
New SMN has the least clunk of just about any Job in the game, isn't at all counterintuitive, is easily understandable, works extremely well within the combat system (having lots of movement, a combat raise, a party buff, and fitting the current 2 min meta system), has satisfactory damage output for the mandatory Caster spot, the abilities make sense within the kit, the GCD system flows smoothly and interlocks perfectly in a full 2 Demi complete cycle, and Gemshine/Astral flow as well as the Primal refreshes on Demi use, which also smoothly slot in the oGCD use of the Aetherflow/Energy Drain system and Enkindle/Astral Flow under Bahamut/Phoenix. It also nails the class fantasy, having both huge Summons that come in and deliver strong attacks, semi-persistent summons that come and fight with you for a short amount of time, and a permanent pet. The only issues at all are that Carby needs SOMETHING else it can do (ideally, it should be separated from the Primal/Demi effects so it's always there) and that the Aetherflow system doesn't fit Summoner's class fantasy and seems entirely vestigial - but since removing it would just make SMN even less, it can stick around for now without bothering me too much, and it's hardly the most jarring "this doesn't make sense on this Job" thing in the game.
Thus New SMN meets the requirements of what makes a job good/well designed, per my perspective.
2) I didn't say it was hard. It wasn't understandable to most people. There was a LOT of nuance. The reason players - and sometimes Devs - were okay with SMN doing more top end damage than BLM despite also having party buffs and a combat Raise...was because it was rare to find anyone who COULD DO IT. Old SMN had arguably the highest skill ceiling in the game of any Job in ShB, and a higher one than BLM did. Proper use of Tri-Disaster, proper stocking of Ruin 4s before Bahamut, BEFORE the ShB changes, blowing even non-damaging oGCDs (like Virus) during Bahamut to maximize Wyrmwave casts, not to mention the danger of ghosting Egi-Assaults at high ping (and when they were oGCDs before made on the GCD in, what, 5.3 or so?) - it was probably the hardest Job in the game. Anyone cay say a Job "isn't/wasn't hard" - "BLM 'isn't hard', you just cast a few fire spells then a few ice spells, right?" - I don't know why people like making that "flex" so often. It was very likely the single hardest Job in the game at the time, it was definitely the hardest Caster. It was also one of the most punishing Jobs for having a KO since you lost all your resources and were completely disjointed from the rest of the party in terms of party buffs and burst resources. Though to be fair...that was
even worse in SB, so there's that.
I didn't say "reading tooltips" was an "insurmountable barrier to entry". I'm saying you can read New SMN's tooltips and understand more or less how to play the Job optimally. Old SMN, you could read your tooltips and figure out how to play the Job...at about 50-60% capacity. Further, this doesn't discount my point:
New SMN is fine in this respect, too.
3) You can, but barely. It's still some of the least jank of any Job in the game, and it's not easy to do. I don't think I've ghosted any of them yet. Use them after the 1st and then 2nd Astral Impulse (Ruin III) and it isn't an issue. You want to contrast that to Old SMN's ghosting issues?
Really?
3b)The flexibility it offers isn't "a joke". Again, if you stop using ridiculous hyperbole, I'll stop contesting you on it. It's not god tier, but it's still real flexibility, which makes it not "a joke".
3c) "3-4 casts/minute"? Wut? o.O
Do you mean 3-4 less than BLM or RDM? Do you mean less APM? Do you mean hotbar buttons that you press? At minimum, counting Gemshine, Astral Flow, DWT/FBT, Enkindle and Ruin 3 all as single buttons (despite them pulling double duty and Gemshine, Astral Flow, and Ruin 3 all taking on different effects that alter their use and parameters such as cast time and GCD/oGCD function), SMNs still use 11 buttons per minute, 12 if we count Searing Light every 2 mins. AGAIN: Hyperbole. Stop the hyperbole if you want a rational and reasonable discussion.
3c) HOW does it "no longer fit with its own lore"? What part of its lore is it violating? Like...be specific. They bind and summon Primals to smite their foes. They gather the residual Aether of Primals to do this. If you mean summing Louis against his will, Old SMN was already doing that. What is the LORE that it is not fitting?
3d) What are you talking about? Granted, you are probably using a SUPER narrow definition of "meaningful" as an adjective for development - probably because even you realize that the Job is quite open to additional "development" with no qualifiers. But even with such a qualifier, New SMN actually has more room for meaningful development than Old SMN did. Old SMN had basically forced the Devs' backs against a wall since it was the ARR SMN with various disparate pieces grafted on that didn't fit the original theme. Original SMN lore didn't support the idea of corrupted "Dreadwyrm" Aether or Deathflare, either. And there was no where logical for them to go.
Dev meeting on expanding ShB SMN into EW: "So...what do we add? Another DoT? Another Demi?" "We can add Alexander!" "Do we do it with another trance?" "Nah, that's too much like Phoenix." "Okay, we'll make it a stand alone summon that fights beside you but isn't part of a Trance." "No, that's what Bahamut does." "Well, we could make it different from Bahamut where it attacks based on the number of buttons you use, including oGCDs?" "No, we USED to have Bahamut do that, remember? It sucked. That's why we changed it." "Okay...well, I guess we can just give Egi-Assaults another charge each?" "And what, raise the cap on Further Ruin? Then people will just stock up 20 Ruin 4s and spend minutes of encounters spamming it, trivializing them." "Well...we could split Phoenix off of FBT and make FBT like DWT?" "Dude...no. We don't need more copypastes." "Well...maybe we could make you turn into Bahamut to do a big attack?" "That's the Limit Break already." "OOh, right. Okay, yeah, I got nothin'."
There was nothing to add. Old SMN was a Frankenstein of disparate and relatively incompatible things that somehow, against all odds, worked, but barely. Any tinkering with it would cause the whole house of cards to fall, and there was no meaningful room for growth or meaningful development for Old SMN. The irony here is that New SMN both has easy paths of growth to implement and logical within its own system:
Next expansion - add 3 more Primals after Phoenix, Leviathan, Ramuh, and Shiva. This is so easy of a choice it practically writes itself. I even pitched once before an idea for what all three would do I made up on the spot that were distinct from both each other and the three existing ones. It's that easy.
After that - add a 3rd Demi, probably Alexander. Could add in 3 more Primals at this point, but don't have to. If they do, Moogle Mog, Ravana, and Bismark would be my choices. "What about Odin or the Waring Triad?!"
...after THAT, Odin and the Warring Triad.

Odin for the Demi would be pretty boss, be like FF13 with a mounted Odin fighting beside you. They could even do a fun little quirk and have him have your name as his subtitle (nodding to the whole killing blow thing from the FATE) and the Triad could be the three Primals for this set. OR, could do a "Sisters" thing and have the Triad be the Demi itself, but I'm not sure how that'd work.
After THAT, obviously the Four Lords. Genbu could work like FFTactics Golem using an AOE party stoneshield in place of Phoenix's Enkindle or Everlasting flight, then you go through the trio of Primals after that.
And at this point, we're talking 12.0, and I've only gone up through SB.
There are PLENTY of options for growth, is the point. The only trick is making them feel different enough from each other, but that's a problem every Job is going to face 4 expansions from now, if not earlier (if not ALREADY). New SMN is actually set up for growth since the system is modular. Expansions can take turns adding a new Primal trio, new Demi, or even both. The core rotation is hyper plug-and-play modular, which makes New SMN possibly the best set up Job in the game for future growth and additions at the moment.
Think about it, what are you going to add to GNB next expansion? A 4th powder gauge and another 2 gauge spender? What are you going to add to RDM, an upgraded visual for your base spells of Jolt 3 and Verfire/aero 3, and a yet another press of the Jolt button at the end of your combo after Resolution? What are you going to add to NIN? WHM? MCH?
There's not really a logical path of expansion for a lot of Jobs in 7.0 right now, which has me thinking 7.0 or 8.0, at some point there's going to be a huge shakeup because there's not a lot of room for a lot of Jobs to keep growing. New SMN, on the other hand, had a modular system that was very likely set up to make expansion easy.
Far from "reeks of being a rush job", it appears to be thoughtfully designed specifically to prevent it being painted into a corner again.
4) "Play like a level cap job then"; that's pretty subjective. Why should a level capped 90 Job NOT play like a level capped 50 Job? What even IS that? That's a horrifically nebulous, undefined term. What makes a "level capped job"? Is it number of abilities? APM? How is that DEFINED? Why is a level 50 ARR endgame rotation now insufficient for the game when it was fine at the time? Many of the same people are playing the game now as did then and enjoyed it then. If a Job plays equivalent to an ARR level 50 Job (or more), it's fine.
5) You may make such an argument - but such an argument is your opinion/subjective, not an objective statement of fact. There are arguments that there should be at least one Job of each role that is super accessible with low depth (again, New SMN has depth above zero) and that such a thing is good for an MMO. WoW Hunters and Paladins were a meme for years, but it were also the most played classes and probably responsible for a lot of "non-gamer friends" joining the community and growing it over time (since people tend to play longer if they have friends to play with, and people sometimes intimidated by complex classes getting their feet wet with simpler ones stick with the game longer, sometimes swapping to a more complex one later and sometimes sticking with the simple ones). One could also make an argument that having such Jobs in the game is actually good for it - provided that it's at least one per role but not ALL Jobs in a given role. At present, this metric is met by WAR (arguably PLD), WHM, and SMN. And there's an equally valid argument to your own that this is a good thing.
6) "I don’t care if there’s a dissenting view as long as it has logically understandable and coherent arguments." - Good, because mine have been.
6b) "popularity" in the sense of "widely played and used" is absolutely an argument for a Job having a place and being fine. It's NOT an argument for depth or complexity - as you say, people often want to play what is easy - but that's also kind of a point against your position that Jobs should be hard. If players actively avoid hard and complex Jobs, that means people don't WANT them. Or, rather, that the majority doesn't want them.
THIS DOES NOT MEAN that hard/complex Jobs shouldn't exist. But it is absolutely an argument for Jobs like New SMN
to be in the game.
7) They aren't "playing things badly". They're playing it well. The Job is designed to be easy to pick up and be played well. Your argument is that people should be forced to play things COMPLEXLY, and that's a different argument AND a subjective one that there are lots of arguments against. A one word argument against it might be "Wildstar"...though there's a lot of nuance there. Another would be "BLM".
Again: You want SMN to be complex because that's what you prefer. That doesn't make New SMN a bad Job. It makes it a Job you don't enjoy.
But more than that, wanting all Jobs to have a higher level of complexity may not be good for the game, and has a certain wiff of gatekeeping to it. Some Jobs being that way is fine - no one's arguing for BLM to be removed from the game, for example - but it doesn't mean a Job not being so is bad or broken or not fine.