A lot of your points makes it sound like you never actually played back in Heavensward and are just basing it off things you read online. Also what you find fun does not extend to absolutely everyone. I've been playing since ARR beta and many things you've stated in this thread I find as needless jank and am glad it has been removed or changed. There are many areas in this game I feel could use improvements, but bringing back old frustrating elements does not make the game more fun for me, it makes the game more frustrating and annoying to play.
Aggro management amounted to being in tank stance for a few seconds then being in DPS stance for the rest of the fight, and I never felt swapping in and out of Cleric stance was fun and engaging. All TP did was limit your AoE damage output, it was about as pointless as MP currently is.
Dungeons were never difficult outside a few of the old ones allowing you to pull all the packs from one boss to the other and being overwhelmed.
What build variety? Do you mean cross-class skills? The skills that only had a few good ones and you were considered trash if you didn't have them? Oh yeah I sure miss having to do tank swaps with other tanks that didn't have Provoke because they decided to go with a different cross-class skill (aka never bothered to level gladiator high enough)...yeah that was definite the peak of gameplay. Or how about those healers without Swiftcast that would just sit there for several seconds trying to revive someone?
You make it sound like skill is meaningless now. Item level always had a significant impact on your performance due to how much stats increase between raid tiers since this game only has vertical progression.
Everything is optional. I can choose to not AoE on packs or only spam a single healing spell and still clear most content outside of high-end raids, but that doesn't mean my party will like that I'm playing badly and significantly slowing things down. Healers were expected to use Cleric Stance, especially since all your damage was based on your INT stat and even since the very beginning healers were expected to deal damage.