Well, nowadays nobody can win CL unless your club is called Real Madrid or Barcelona, he played for the latter club. And which team he should've chosen in 2014 after Suarez arrived and he had no place in the squad?
Competing for the CL doesn't mean that you magically have to find yourself slotted into a contender's lineup. It's a process. He chose to go to Arsenal which is a club with no ambition whatsoever other than a top 4 finish and an FA Cup final. It'd be far better for him to force a move to any sleeping giant he wanted (eg Inter or Milan, Valencia, Liverpool), or even a team like Juventus who was trying to compete for the CL at the time, or Atletico Madrid who needed something more to dethrone the Clasico giants.
If a player like Sanchez in his prime goes to an ambitious or recovering club, he can bring positive side effects to that team. Players will want to play with him no matter what the club's situation is. Surely mismanagement of big clubs has played a part in their decline, but if players will only go after the money and the status quo, things will never change and football will die as there will be more demand for 'Superleagues' and less demand for variety in European football.
The problem is that players don't see this because the agents run the show. And agents will follow the money, they won't follow ambition or career progression. Look at how Wolves has harbored so many young talents now. An agent is running the show. 3/4 of those players would laugh at the possibility of joining Wolves, let alone in the 2nd tier, but an agent orchestrated those moves and has created an environment where he can sell these players for more now. Several years ago a player would play for a shirt he loved or was attached to. A modern day Batistuta would not stick to Fiorentina in Serie B or not participate in Europe for years. But the actual one stuck for ages until they had a team that participated in the Champions League.
We got possibly the best player of all time at his prime from Barcelona whilst participating in the Uefa Cup after barely finishing 3rd in Italy 20 years ago. Do you think it was possible for Milan to sign Mbappe last season? That's pretty much what Inter did back then x1000 in terms of difficulty. And it's not just that "football is changed" and "players/people are different now". It's simple. If players wanted to run the show, they would. But they love the fact that they have these agents running it and are maximizing their revenue. There's not many players to feel sorry for. They will be the ones regretting their choices for an entire lifetime when they realize that the marginal difference in income that they enjoyed was not worth throwing away their potential.
You're Alexis Sanchez, probably a top 5 player in your generation, definitely top 10, and you waste your career at Arsenal and then when you have the chance to escape that, you move to Man Utd and all that because Barcelona deemed you surplus. I mean how the fuck do you explain yourself to your grandkids? Depression doesn't really cut it.