That’s a very good question, and I can only answer for me and the people around me:
I am doing this right now. I live in the open world and literally have a quest log full of dungeon quests that are taking up space until I can do them as follower dungeons. I am the target audience for both follower dungeons and for delves, so here’s my opinion on things.
It’s the outright codification of “this is a valid endgame path” through how it’s been presented. Delves and the overworld are getting a lane in the vault. It’s officially validated and a comfortable spot to stop.
The faster people “know their limit and play within it,” whether those limits be gameplay skill or social batteries to deal with “hell is other people” for the sake of pixel numbers, the happier we’ll all be.
Again, maybe I’m just older, maybe I’m coming at this from a minority perspective, but I watched friends around me, lapsed players, light up and re-sub when delves were announced. It’s for us, it’s supported and validated, and I’d bet money that we’re not alone in this.
Some people will be slaves to “keeping up with the neighbors” forever, absolutely, but for those that can shed this and read what feels to me like intentional writing on the wall, this is the ticket out of the “decline dirge” of M+ PUGing, and the “game of favorites” of socially unhealthy (which is not all) raiding.
There is a place for M+ and raiding. I think it’s been mischaracterized by waaaay too many people. It’s a content type for groups of friends and people with thicker skin. The way you fix “no one’s taking my class” isn’t done by anything you can do to M+ or Raiding itself, you do it by adding options.
All one has to do is… accept a smaller number on their gear.
As someone already there, I can tell you, it’s blissful, and I can’t wait for more content to enter my space. I just have to wait a little longer!