One of the problems you mentioned was really visible at PSG apart from the perhaps less than harmonious relationship between the star players who were already in the PSG squad at that time. However, everyone also sees other things, such as the age of the star players who are no longer the same as before when they were at PSG and also the easy competition in Ligue1 for PSG to win the League every season. So that the players' skills and enthusiasm do not develop when playing in the Champions League.
PSG's problem may not lie with management because management has made several efforts to bring in star players but the problem is not only recruiting star players but PSG needs players who are really needed and are solid. It's useless if there are star players, if they can't be solid then the club will remain not being able to play optimally, too many star players, sometimes it's not good, will cause internal personal problems and the players play selfishly on the field just to show their best performance individually, but that is actually the club's fault because you can't create chemistry so that the star players can play solidly and pampering the star players too much also makes the other players feel like they are not valued and the star players become arbitrary.
A club like PSG needs a strong push, not only about recruiting great players, but also requires equal competition in its own league and harmony between players so that the club can work together well. Apart from that, don't change coaches too easily just because you haven't been able to win the Champions League because of that. It's not easy to find a coach and he also needs time so that the club he coaches can perform according to the fans' expectations.