Powercreep has made you able to skip mechanics, so why make the mechanics in the first place.
This bothers me a lot, particularly for previous expansions. Gear progression is important when the expansion is current, but it is irrelevant for previous expansions because everyone can just get max poetic gear, so they may as well sync them to minimum IL.

Mob packs/most bosses are meaningless because you have overloaded kits and the potencies of dps skills are too high.
That is mainly true in old content because it wasn't designed for the current potencies.

There is no danger in dungeons, most normal trials and now in 24 man content.
Not really true. I've seen multiple full wipes in the previous normal trial and the current one does often lead to a death on people's first time. The more accurate statement would be that they stop feeling dangerous once you understand the mechanics, which is when it's no longer your first time. They do telegraph things more now though, and telegraphs make it significantly easier compared to content where they are removed like Extreme, Savage and Ultimate.

I do not feel that normal trials are challenging enough for me personally, so I do the extreme versions.

Having more states of failure makes gameplay interesting.
I agree. I especially think this is relevant for solo duties where you are not relying on others. It's alright to struggle with duties such as In From The Cold or following characters in stealth because that's what a video game is (yet people on these forums have complained about the difficulty of these things).

Making everything too easy develops a toxic mindset as well (class responsibility, laziness, babying players, no responsibility over anything).
Making everything too hard develops a toxic mindset as well (demanding people watch guides and know all these things that they didn't know, just so they can complete the story and watch a cutscene).

Class interaction is nonexistent. Tp/aggro/debuffs offered varying gameplay.
I'm all for class interaction, but the examples you mention here are not good ones.

TP was mostly useless and you would only notice it if DPS was extraordinarily low while doing AoE or if you accidently pressed Sprint in battle.

Debuffs applied to players were useless and mostly just a nuisance, such as mobs applying random paralysis, sleep, silence and stuns on you and you didn't even know which enemy did it and it interrupted your strict rotation. Players applying debuffs to enemies is alright if it's like a DoT or a stun, but when it comes to slow, sleep or bind they are virtually not on people's hotbar.

Aggro was alright, but it was complicated to explain this to a new player. When someone starts tanking, they are usually afraid of it and have anxiety, so when you started explaining all this stuff like enmity combos and stance dancing, it confirmed their suspicion that tanking is hard (even though it's not). We had a massive gap between people who played tanks exclusively to spam enmity and people who played them like a DPS and it didn't feel right to have such a massive gap between player performance.

Why have different classes if the gameplay is almost the same?
Glamour, animations, is the obvious answer.

Chat interactions are shunned because of the tos rules and the rules are babying people. Shouldn't we try to let people resolve situations themselves
The problem is that many people in this game are not capable of resolving it themselves because they are unreasonable. It could be for various reasons, including personality disorders or substances they take, but it is fairly common to meet people who are just not chill, reasonable people.

I was once in a party with someone that I agreed to do a dungeon with and as we went through the dungeon, they stunned me by berating the tank constantly. The tank didn't do anything wrong and they kept quiet until near the end, then explained they had farmed dungeons all day without any problem. The truth is that the person I was in a party with just had aggression issues and was being unreasonable.

People grow when they get to resolve things themselves rather than trying to limit them with arbitrary rules that make them feel caged
I've heard it was really, really bad in games that didn't police it such as WoW, LoL or Halo. I didn't play them but they have a certain reputation... https://youtu.be/8cMkQRBknto?t=133