Why do so many hate the Multiverse idea now?

Serious question since I'm kinda behind on some of the updates and discussions.

There seems to be a lot of backlash regarding the multiverse and variants of late. Why though?

I thought we always wanted the X-Men and Spider-Man to be a part of the MCU canon to fight alongside the Avengers. And this plot device finally gives them the opportunity to do so, right?

Sure, we've not gotten that many hits of late, but is that because of the multiverse as a concept? Or is it just poor usage of the multiverse device?

Can someone fill me in?