Difficulty of normal content.

[jdtuggey]

Spoiler warning for Endwalker and Dawntrail

For the first boss of the first dungeon, there's two patterns, they are always the same. Once you figure them out, you know exactly where to move next. I had them figured out after having ran the dungeon something like 3 times.
There's even one pattern that takes you directly to the boss' face, and you're safe there until you need to move for the final AOE.
The other pattern requires you to move to one side, then the other, then loop back around to the first side by moving back a little bit.
One thing that might help here: You're often better taking an AoE to the face than trying to move out of it and risking getting hit by 2. I often make that choice consciously.
(I mostly play melee since DT, there may be other solutions for ranged)

Vanguard's second boss AoE's are targeted at players. You just need to relocate slightly. You also don't get vuln stacks for getting hit there afaik, so they're expecting you're gonna take a hit or two.
Stop dps if you need to, focus on avoiding stuff, not like there's an enrage lol.

Concerning Skydeep Cenote's bubbles, you're probably moving too much during bubble phase, or others are, which endangers everyone else. If you move slowly and you keep to your quadrant, they're really easy to manage.
People have figured this out at this point, and they don't run 5 yalms to avoid one anymore.

M2 is a bit harder to manage (I would expect that), I haven't done it enough to notice a pattern, and I've died on this, but judging from other similar fights, I'm pretty sure there is one.
There's a perspective bias in humans concerning randomness, we tend to see an even distribution as "random" and a truly random distribution as not so random.

Big cheese is the last boss of Smileton, btw. Last boss of Subterrane is Golbez' friendo.
Antivirus telegraphs its attack -clearly- like 20 seconds before he does that phase. That's when you need to calculate your pathing, not while it's happening, and you need to process that mechanic as one block.
Again, it's always the same patterns, and they're designed so they always take you to a place where you have space to avoid immune response, because it's not random, lol.
You only really need to focus on nailing the X's and O's. They're all conventional telegraphs. The shapes tell you exactly what's gonna happen.

Concerning Valigarmanda, well, we've always had telegraphs where we need to look at what the boss is doing, like the first boss of origenics clearly telegraphs which side is gonna blow up by lifting his arms.
Usually when I fail a mechanic, when it comes again, I look at things that might be it. Castbars or boss animations are the #1 prime suspects in all of these cases.
I also feel like you should know these things if you're doing 90th percentile parses. Of course, no way to verify any of what you're saying because you're hiding on alt, so #doubt.

You mention Amon, sure he telegraphs firaga with castbar, but does he telegraph strophe with castbar ? (͠≖ ͜ʖ͠≖)
You don't seem to have a problem turning your camera around on that boss.
The first boss of Vanaspati also has pretty non-standard telegraphs, and asks you to look at the boss/castbar while they are resolving. That's fine to you ?
Same with the last boss, like, the meteors resolve really quick and barely leaves you time to move between the 2nd and the 3rd. There's a bunch of circle AoE's sprinkled throughout too.
There's also a lot of overlapping mechanics.
Hermes has a butt ton of "non-standard telegraphs" too, and you don't have a problem with those.
Perhaps because you got used to them ?
Add second boss of tower of babil to that, you need to look which head isn't on fire on the second boss of ktisis.
I'm sure if I think hard enough, I can find plenty more.

Concerning the speed of some of these mechanics, it certainly caught me by surprise, but I got used to it. Doesn't feel "faster" anymore.
I never felt your problem is a matter of skill, I feel it's a matter of not wanting to. This game is pretty easy, really. At least at this level. I know without a doubt that you can do it.
So many people have given you solutions, and you're just like "nope" and you keep re-emphasizing the "problem".
Like, people have been here spending their time explaining and telling you "you can do it", and you just brush these people aside as meanie pawns of Arthars and you play the victim.

Dawntrail didn't slight you, you're slighting yourself lol. You've clearly demonstrated there's a matter of attitude in this post alone, that you feel your mistakes are others'.
I feel like the first step to resolving your issue is to take personal responsibility for your mistakes. When you fail a mechanic, it's not square that made it too hard or others screwing you up.
Owning up to these mistakes and learning from them is the first step to you enjoying DT, I think.

I don't know why I am wasting my time. ._.
When a game doesn't work for me, I am more than happy to not play it. It also sends a pretty clear message to the people that own it (square in this case).