How many veteran players have started a new character since the ARR revamp was implemented in 5.3? Most haven't experienced what it is now. They're just making comments based on how it used to be.
The streamlining has greatly improved 2.0 as an introductory experience even if it's still not HW quality. It's not surprising the new players are enjoying it.
Some might. Others will stick around. It depends on what they want from a game. Not every content creator is obsessed with end game gear progression despite the impression you might get from more popular streamers.
The game has thousands of hours of content available to choose from. Those who are looking for more casual game play won't lack for things to do even after hitting level cap.
SE added a substantial amount of crafting/gathering specific content this expansion. They're adding Island Sanctuaries next expansion.
I don't think we need to fear that they're going to fall into the trap of focusing on end game, especially as everyone watches WoW dying because it did.
