I think they've had a number of controversies over the years, but I think the big frustration people have at the moment is really just that snaps are kind of a crummy thing in several respects, don't have an open source backend, and often don't work as well as flatpaks (to my understanding)

The increasing commitment to going down that path is a big turn off for many, and disqualifying for some.

That being said, I have used and been happy with Ubuntu in the past. I think some of the dislike is just motivated by "thing popular", especially since it's so popular with folks new to linux who are still figuring things out