Basically. Only 3 classes in 16 years. Those just aren't good odds at all. Adding new classes requires re-balancing everything, and we have seen how it takes whole expansions for them to not feel broken. And I don't see this changing anytime soon, so I'm really not up for waiting for years for the possibility of the new class being the one I like. Considering how much of a struggle they have implementing them, they will most likely go for concepts that offer new and interesting gameplay over lore concerns.
So much like AR's, Class Skins would offer that personal immersion and fantasy without affecting gameplay. It's the most efficient way of adding fantasy and immersion for their sake, because as much as those are my main concerns, I can't deny they should not be the priority when adding what is essentially something that affects gameplay so deeply.
So I will take a "Necromancer" that is a reskined demonology Warlock that summons undead instead of demons.
Heck, if they want to add a gameplay effect, it could be interesting to play with altering the magic schools with these skins.