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.
I think their coach is pretty good. Just look at the history of the PSG coach. The average age of training them is only 2 to 3 years. In addition to the atmosphere is not conducive, it seems that PSG cannot make the players mentally work hard. They seem too comfortable with a large salary and good facilities since changing owners. Maybe PSG can change the format of the coach for a longer term. For example, 5 years or 10 years. Just look at Man City, it took them about 7 years to get the UCL cup with Man City. For PSG's local league class there is no doubt but for Europe they are still weak. 