No, you don't have to memorize, but it sure helps a lot, because you're multi-tasking combat too. So if you know the next 3 moves that are coming up you can prepare for them and focus more on the combat.
Once again that comes down to bias, this may be easy for you, you are probably a very skilled player, but for many others they need to memorize at least the critical sections or they get overwhelmed.
Ok sure, the main flaw with this post's reasoning is that it ignores TIME
Not completely true, the OP points to many mechanics, we are using Titan EX landslide and Twintania divebombs to point out that insta-kill mechanics negate any ease introduced by overgearing content. You can overgear all you want but one mistake by a party member and you're dead, iLvl 75 or 200. One of my central arguments is that on release of new content, these mechanics should insta-kill anyone, but after some time, gear should allow you to survive it. This requires balancing insta-kill mechanics to be just very high-damage mechanics - kills anyone at the intended iLvl, but almost kills anyone overgeared.
Agreed, they want to circumvent challenge, what's wrong with that I ask? Why do games have an easy difficulty, normal and hard? Because some people don't like challenge, some people play RPGs and lvled up to 10+ what's needed for the boss so they can crush it, I'm sure you can think of a friend like that. We're not all hardcore gamers, some of us want to relax, and have fun and hang out with the community. Surely you must understand this, if FFXIV wants to keep its subscription numbers we need to keep those people around. They usually play less too, probably just reaching that content 3-4 months after its release, why not let them beat it more easily? This is not a race, let them run at their own pace, people need to stop thinking it's a race, it goes back to that WOW developer's post, this breeds a toxic community, which we have now.
This here, is the biggest fallacy, this ties back to the issue of time, you are forgetting there are months between when content is released, and when gear catches up to allow them to survive high damage mechanics.
1. When content is released, the scripted mechanics are so punishing, they may as well be insta-kill, hardcore players, will need to dodge these or face a wipe, the game will be just as hard as it is now for newly released content. But there can also be random mechanics that do less-damage, the trick is a healthier balance between scripted mechanics and random attacks, now to hardcore players this balance doesn't matter, they are good enough to adapt. Challenge is the same, there's less you can memorize for, but more you can react to, I'd personally enjoy this and I know many others will too. The scripted/random mechanics are still the primary determining factor of the fight "for now (new content)"
2. Now as casual/mainstream players catch up, MONTHS LATER, gear wise they will have an easier time, allowing them to survive a few more mistakes, as time goes on, even the most casual players will stand a chance.
Here's the problem, it's not balanced in this way, the mechanics are the primary determining factor in victory, and always will be, years after content release unless they fix insta-kill, miss a divebomb, you wipe your party, end of story.
We are not asking for extremes, we are asking for balance, not make it 100% scripted or 100% random, allow mechanics attacks to scale slower than gear, so that gear can "eventually" ease the fight. So properly address easing the difficulty of fights, a blanket echo stat boost was just pure laziness and doesn't help as the OP pointed out.
So coming back to this, nope, balanced content will be difficult upon release, and does not ignore the problem of "recognizing player skill", balanced content will also scale better with gear, so after a few months (TIME) maybe more, it will also address the problem of "casuals feeling left out".
And "battles are no fun"? Fun is subjective, fun is defeating something "the person playing" finds challenging, and what's not challenging to you may be challenging to others and fun for them. I played hardcore too once, I admit I had a pure definition of fun too, playing a game at the top-tier was exhilarating, challenging and victories were so much sweeter. I was arrogant too, I felt that, everyone should experience this awesome feeling, but as I talked to more and more people I found that lots of people were normal and had modest goals and enjoyed just crafting or slowly progressing. And the more I got to know them, the more I understood, that this game isn't accepting to these types of players.
So I'll tell you what's not fun, being elitist and subjecting casual players to the same arrogant standards you have for game difficulty and assuming because it's fun for you, that if they just worked harder they'd experience the fun that you experience. I'm sorry it doesn't work that way, they are just getting frustrated and giving up and quitting, sure some players improve but that takes dedication, time, practice, etc... Not something casual players usually have the time for.