Ehm, what?
Hunters are one of the overall best classes and looks to stay the same way in Shadowlands and shaman got a redesign for mainly enhance but also elemental.
Mages might have turned out silly with corruptions but they really weren't that good before that and they are not among the most played classes at top tiers unless you can stack crazy amounts of stats (you can't in Shadowlands).
What are you on about? Have you played it yet? You seem to have litteraly no idea what you're talking about.