In part, I believe that’s why Classic was made a reality. If you truly liked how the game played then, if that incarnation was what appealed you to the title, then its there for your consumption.
I have a slightly different take here.
I don’t think its about the expansions as a whole that have hurt the game. They have given Blizzard a chance to refine parts of the game in a positive way that I truly think are genuinely better today than in the past. So it isn’t all bad.
If you ask me, things like Artifact Weapons, Azerite, Essences, and Corruption are what I think have truly hurt the game more than anything else.
The power that these recent tertiary systems provide is enormous, so much so that if you’re even the slightest bit behind, you’re perceived as dead weight.
I don’t think you have to start an entirely new variant of WoW to address the vast majority of the concerns you’ve listed.
Design Problems
These are already being fixed as the game gets patched. The issue here is that what you view as a design problem may not be by the next player and so it becomes different to iterate on things that no one can agree upon in the first place. Inherently, some will be happy while others will not.
Power Inflation
This can also be addressed easily by simply stepping back and re-evaluating how character progression works. We already undergo a squish every so often, a squish that essentially negates the power progression one had in any prior expansion so much so that we hardly see any form of progression at all under end-game as we shift from tier to tier.
All the other points you’ve listed, I don’t grok why a new incarnation of WoW is necessary in order to iterate upon whatever problems you see and to make those better. But again, I can’t stress enough my initial point about design problems above — at some point some will be happy, others won’t. Nothing is ever perfect and will satisfy everyone.
You seem to act as if our subscription fees are just being tossed into a bank account and not being used. Over those 14+ years, Blizzard has had to pay their employees, upgrade hardware, maintain their network infrastructure, provide work facitilities, insurance for employees, paid time off, licenses and software upgrades that employees use daily, etc.
In short the cost of running a game studio of any measurable size isn’t cheap and there is a significant amount of overhead that goes into WoW that you seem to want to overlook.
Also the development of a new engine or title isn’t cheap. You need a drastic up-front budget to cover all the R&D costs for that effort and you won’t see any returns on that investment until 3-5 years down the road typically.