They are pampered and rewarded too young without actually achieving much. A young player comes in the side and one good performance, they get a new contract and a payrise.
Yes. But this is pretty much a generic challenge, for any club at a reasonably high level, these days.
I guess what I'm suggesting is that if there's a bad culture within a group of players (doesn't matter what it is, precisely), it should be a primary task of the manager (at a club like United, that is, where there is no DoF or similar figure around) to address this.
So, the question becomes: did Mourinho try to fix the problem - only to be undermined/not backed up by his employers (that would mean Woodward)? Going further back, did LVG try to fix it? He's made some unflattering remarks about the structure at United too - but he hasn't said anything specifically about a rotten culture among the players.
On the face of it, both LVG and Mourinho should've had the authority to take on a rotten culture. They wouldn't have allowed themselves to be pushed over by any "clique" of players, I really don't think so.
Obligatory (but somewhat relevant) Fergie reference: when he arrived, he faced a culture problem (a major one). He made it an absolute priority to fix this - and he was backed 100% by both Edwards and senior/heavy figures like Busby and Charlton.
Another question: is there any reason to think that Fergie's successors have tried to address a core problem (a rotten culture) - but that their efforts have been undermined in any way?
. I don't see him ever being back in the PL, PSG and Inter are his only realistic options.