This is complete nonsense. Let's assume someone only likes 1/3 of specs, for various reasons - that doesn't mean everyone like that likes
the same 1/3 of specs. Which means adding a new class/spec every other xpac wouldn't even help those people, because it'd have to be something that they're actually interested in to begin with, but furthermore it'd only ever help SOME of those people even if you do it. And that's every two expansions, which are on at least a 2-year cadence. So every 4 years you get a chance of MAYBE having ONE new spec you like? And if you don't, that's an 8 year interval until you maybe like the next one?
And you think that's a solution? Rofl.
That's a perfect argument if your goal is to actually run a profit-making company.
You know what "isn't [a] valid argument"? Telling your customers "you getting bored is just a you problem". Because they'll go "you're right, the problem is me - me quitting the game".
Your goal appears to be "how to make WoW into what I like the most", whereas REALITY is "how to make WoW into what makes the most profit" and that usually goes via the route of what
most people like, not what @
WowIsDead64 likes.
Which is precisely why they keep changing existing classes all the time, rather than leaving them all the same to make you, personally, happy and piss off legions of other players.