I've never been a fan of MMOs, so I don't have much experiencewith Transmog systems. The first time I encountered one actually was in Assassin's Creed Odyssey. And I LOVED it instantly there. It let me make my Kassandra look how I wanted her to. There was a particular armor set that I really liked for aesthetic and story reasons, and instead of having to leave it behind when its stats no longer kept up with my level, I was able to keep it around longer. I think this sort of system provides a genuine roleplay avenue in the form of giving our character their own signature look and allowing changes to feel a bit more like in-story decisions.
I've never really LIKED the constant changing of equipment in crpgs. Usually it's just a neutral fact of things, but I hate when a companion character starts with a unique armor set but then I have to get rid of it because it's all too weak. I love when games allow characters, in particular companions, to keep their unique style. In Dragon Age: Inquisition, I was delighted that companions basically had two unique outfit styles thatthey could alternate between, and that our Inquisitor was also the same in that regard. So yeah, that's why I support a transmog system.