I think the change is fine.
It's a bit silly to see people gear swap on a pull-by-pull basis, especially with tank trinkets on DPS. Now you just choose your best overall set for the dungeon, just like with talents.
People whining about losing depth or whatever are honestly just clutching at straws. What depth? You already know ahead of time what you're going to wear depending on the pull/boss so it's not like you're some sort of genius because you have 10 different sets saved on Opie or whatever. In actual fact, making do with what you have equipped on pulls that are less favourable probably requires more thought than pressing a bind to select a set.
If you really enjoy having 10 different sets in your bags then I guess you're losing out, but I honestly feel like this has been turned into a way bigger issue than it should be. And it's not gong to change anything anyway - you already don't take a Shaman or whatever to high end M+ because their survivability sucks, that should be fixed through helping the class overall, not wearing a fucking tank trinket as an Elemental Shaman.