The reason for PSG they spend lots of money but they can't get anything in the champions league is mostly because they didn't have a good manager and they just bought superstar players while PSG didn't have a balanced team, this situation made chaos in PSG that's why they players couldn't have a good atmosphere in the team to have good performance.
You made a valid point here, even if a team gets all the most expensive players in the world, they can’t succeed without a good manager to manage the team well. When PSG signed Messi, Neymar and Mbappe everyone thought they’ll be unbeatable and they will win the champions league trophy for the first time but all proved to be futile. A coach like Pep Guardiola will be able to manage that team very well to the champions league final. Now all the players are separating, I don’t know if PSG’s dream of winning the champions league will be fulfilled dream soon.
The case of PSG with lot of quality players with nothing to show for it at the champions league is the same as what happened to Chelsea this previous season. Too many talented players but couldn’t put them into good use becomes a wasted effort and resources by the club.