Stormblood(which, honestly, was the height of raiding due to how well designed jobs were at the time and their application aside from WHM)
I felt that Stormblood removed most of the jank and useless actions and ideas, but there was still a bit which Shadowbringers cleaned up tbh.
what happened was the butchering of DRK's identity
Well I would say the focus was changed from the Abyssal Drain heals over to absorbing things with TBN. I can understand why they moved away from Dark Arts just because it was meme'd so much by the community. To be honest, I always liked Dark Passenger and wished it had more involvement so getting Flood of Shadow to use regularly felt really good.
jobs becoming more Warrior-esque for Tanks
Well 50% of people using tank stance 100% of the time, and the other 50% using DPS stance 100% of the time, combined with how it was hard to explain enmity combos as a concept, made it understandable to me.
Healers nearly playing identical to WHM(hence where people started complaining about 1111111 spam in Endwalker)
Arguably, WHM had multiple DoTs in Stormblood though, although I'm not quite so sure they had intended them all to be used like that which is why they made an upgrade system.
Since then, we stepped into the realm of 2 Minute Meta where everyone's buffs/debuffs are all burst at 2m for raid design
It's sort of logical because raid groups were already aligning them and giving themselves an advantage over those who did not, then complaining that raids were designed for those who did not align them. Their solution? Force them to be aligned so the raids can have an equally tight DPS check for all players. Personally I'd rather they just remove raid-wide damage buffs so that jobs don't have to be designed around this boring 2-minute constraint, or make it so only 1 role type has a damage buff and if you have multiple of them you lose damage.
the FURTHER butchering of DRK
Doesn't feel that different in EW, other than the 60 second constraints.
the uprising of WAR to its current state.
It kinda made sense to increase tank survival with the incoming damage in EW leveling dungeons and to balance the other tanks with WAR and DRK, but it really went overboard to where healers are flat out not needed at all compared to HW and SB. Hopefully this will be fixed.
While PLD wasn't AS crazy, it could still outlast an entire boss fight if managed carefully.
Well honestly PLD has always been one of the first to be able to solo stuff due to Clemency, but obviously that required sacrificing damage and now they don't even need to.
Goring Blade DoT was gone, and instead they made Goring Blade similar to Blasting Zone - hit it and forget it until it comes back up. This kind of ruined people's identity of PLD while others welcomed it
Functionally, PLD is GNB now but with less weaving, like how WAR is DRK with less weaving. But I think its "lore" identity as a holy knight with a shield/sword/desire to protect remains tbh.
When we go into Dawntrail, I'm seeing more of the same
I think what we are seeing is a solution to replace DoTs or other keep-up buffs by using symbols or Dragon Kick > Bootshine type mechanics to make multiple combos relevant. Hopefully that will allow PLD to feel like more than just Royal Authority spam for example. It looks like Atonement will become like a second combo and a further double down on the Requiescat/Inner Release-enabled attacks.
Why is that since Shadowbringers?

It's because the Development Team is scared of job complexity.
I think it is because of balance and accessibility both.