changes to the game that would go hard

[Jeeqbit]

move away from long, linear rotations

I don't personally agree with this. I used to enjoy Paladin's long, linear rotation before it changed in mid-Endwalker. I still enjoy Dragoon's long, linear rotation as well. Not all jobs should be long and linear; it's fine for some of them to be proc-based or whatever, but having options is good. Maybe if they go ahead with the skill tree idea in 8.0 they can give people a choice in this area.

diversify cd timers and durations

Agreed. It would help if they just made them all align at 6 minutes because then different jobs can have buffs at: 15s, 30s, 1min, 1min 30s, 2min, 3min - and all would align mid-fight for the DPS check. Or they could just get rid of party-wide damage buffs and stop them being multiplicative.

these could give thematic cantrips/effects from the raid, like:
-giving MNK a somersault dropkick oGCD that works like SAM's backdash
-maybe SMN could invoke Ixion or something in their primal rotation

Seen suggestions like this before. They could drop rewards that give unique effects to each jobs from duties. The only hope of us seeing it is probably 8.0 when they rework leveling and power gain, as well as look at job uniqueness. The potential issue I can see SE having with it, is that they don't want to be stuck revisiting rewards from old content for new jobs that they release. But they could just stick to making improved power versions of the same things in each expansion too.

we don't need learning phases five expansions in

I think this is aimed at Returning players tbh. So a player that has been away for, say, 5 years and last played in Shadowbringers. You might say "but that's quite far into the game" but if they haven't played for 5 years then...

I think it is also trying to solve a problem the game had a long time ago where it didn't explain mechanics at all, so a lot of players just never came to understand the mechanics ever and it was predictable they'd cleave you with everything and give you 5 vulns stacks. The result is it became a backloaded solution where the greater difficulty was in ARR and HW. They're slowly revisiting that now as well.

I think they are trying to revert to ARR and HW design again to some extent, so according to what they've said they are trying to enact your suggestion already in Dawntrail, but how successful they are at that is for everyone to judge or otherwise remains to be seen.

mobs all blend together because they all do the same thing (nothing)

They have actually made more dangerous mobs sometimes. In Dohn Mheg, there are some enemies the tank interrupts to make it WAY easier for the healer. They can choose to do a really large, dangerous pull at the end. In The Twinning, some of the mobs have interrupts that also make it easier on the healer who already is frantically keeping the tank alive at the start. You can prevent a pretty devastating raid-wide for the healer in Akadaemia Anyder.

Even in the latest dungeons there are some examples of different enemies. Tender Valley starts off with a big cactuar and one of the casts sprays needles that takes most of the tank's HP if it hits. It's easy to get hit as well because the mobs are all doing AoEs and it's hard to distinguish them from eachother. The end of Stayborough does something of a heal check with all the raid-wide spam and you can do a lot to mitigate it, including stuns, reprisal, Arm's Length and raid-wide mit.

They have shown they can make some interesting trash in criterion as well.

max level versions of all current expansion dungeons with a progressive difficulty system, like dungeon talent trees/affixes (WoW's M+ and VP2's Sealstones for example)

It would be nice if SE harnessed their old content in ways like this, across the board really. But their solution is always to make a brand new version instead: Hard Mode dungeons were brand new versions. Variant/Criterion are brand new versions as well. They seem resistant to just making use of what they already have when it'd instantly create more content for people.

new crafted sets are equal to previous savage tier, rather than better

Agreed because it feels awful to shed your savage gear and replace it all with crafted gear, after what you did to earn it - enduring wipes and potentially PF for weeks. It just doesn't feel good.

remove positionals

I feel like people come from other games and just aren't used to these, yet they are one of the few things the combat system still has left that were part of what people liked the game for in the past. There are plenty of jobs without positionals and they made doing them have a very minimal overall impact compared to the past anyway.