I think Unchained is an interesting experiment in trying to find a different path - one that isn't the "new edition" or "old edition" duality, but something in between or a third way.
I don't think UC is the final answer...but maybe Paizo is clever enough that they can develop a truly compatible option for those of us who find the current rules a bit dated and a bit too "anything goes."
One other point: Before going the nuclear option route of Pathfinder 2.0, there is often an intermediary stage for companies wanting to freshen up a mature game, and that's creating a new setting.
Golarion works really well for a lot of people. Though I like parts of it just fine, it's never been my world of choice. But set that aside. Even if you love Golarion, wouldn't it be cool for Paizo to launch one Eberron or Dying Sun or whatever setting?
Using the new setting, you could set some boundaries about which rules are canon in that play space and which rules are either optional or verboten in that place. Not a permanent fix, but it might clean up some of the weirdness and extend PF's life by another five years...
I know Paizo has been resistant to the idea of creating a new setting, wanting instead to pack everything into Golarion and its cosmos...but maybe it's time to rethink that...