I can understand the issue from both sides. Not getting any new abilities for like 2 expansions in WoW has suuuuuucked so hard. It feels like your character is stuck in neutral and has no growth at all besides numbers, and numbers are boring.

However, you can't just have more and more abilities growing for all eternity.

I think an easier short-term solution would be to wipe out a bunch of the less useful role abilities and stick to the core ones. Clean things up a bit. Maybe consolidate some of the redundant class abilities into a single button press. Not too much, just a little trim here and there, and then it's easier to launch new abilities.

I would rather have to relearn my entire class each expansion than have another MMO where expansions cause no character growth/change. This would obviously be different for every person, clearly some people prefer the comfort of their character always playing like their character. However, the lack of meaningful advancement or change (aside from getting weaker and having a lesser toolkit, actually) drove me away from WoW. Keep things fresh!