1) devs have stated they're not interested in making Mythic+ type dungeons. there is already too much gear in the game, adding more than what is minimally needed is too much extra work.

2) taste is subjective. designers have an aesthetic they want to implement too.

3) this is a theme park type MMO. everything is done in instances. i don't know how you've missed this point for the last 6 years.

4) you think you want this but you don't. people will ALWAYS go for the path of least resistance, they want their dungeons to be fast and efficient as possible. pull wall to wall boom done. you will not get most people to be like "let's explore this way", you'll be kicked from the group for wanting to deviate. people HATE totorak for all the pointless debuffs that are placed in there.

5) the fate rep system was introduced in 5.0 for this, but once you're done, then eh back to same old. and again this is a theme park mmo, you do everything in instances.

6) new game + mode is just for replaying story. they haven't said whether it will grant exp or not, but i doubt it. besides running roulettes every day gives more than enough exp to level other classes at a relatively fast pace.

7) people complain about trash they took it out. i don't see them putting it back in. Door bosses people don't like them either.

8) this is a system limitation - there's only so many customization options that can be added to characters.

9) they're adding a new frontlines mode I think in 5.1 (seal rock 2 basically from what i've heard). they will never add open world PVP. that's what the wolve's den is for.
if you want old WOW go play classic.