We may need to have to wait until players like Messi, Suarez, Busi, Pique are done to build a new team. Let age do its thing basically. They lost motivation, became to powerful in the locker-room. Basically, they are overpaid superstars who don't work as hard as they should be, and who are basically un-benchable by anyone except managers with balls the size of Jupiter. We're not likely to get a manager like that under this board.
If we fail this season in CL again in the same fashion as in the last 2-3 years, then it's pretty clear that the core of this team is done in the Champions League.
This doesn't mean we can't still do better than Valverde. Problem with Valverde is that he is poor in multiple areas. I would accept 1-2 problems, but basically, he's average in multiple zones. Not good with young players, doesn't play beautiful at all, panders to star players, doesn't rotate. Man has too many faults for a team like ours.
I like Setien but don't think he has the guts to deal with all of our key issues, he can improve us here and there but not as a whole. Would still improve our game visually, would develop players more, but wouldn't handle the stars better than Valverde is doing I think. He isn't a big name, so there is little chance he'd show enough personality to command a star-studded locker-room like ours.