This has been the kryptonite for PSG for many years now. They always try to do as well as they possibly could normally at league, and most of the time they do win the league as well. However, they always end up being bad at UCL and I have absolutely no idea why they are worse. This isn't about just not winning, of course it is normal not to win UCL because you face so many great teams, but it's also about how they are playing worse at UCL than they play at league, if only they played literally the same at UCL as they do at league, they would have been at finals last year for example, or be better this season.
The problem isn't about how they are not winning, it's about how they suddenly become so much worse at UCL, they need to figure out the reason for that, even though they changed many managers along the way, they are still worse, so it is not about managers, they changed players too, so it is not about players neither, it is something else.
maybe related to their mentality. PSG can play well and very strong in Ligue 1, even always dominating. They have high confidence to win the match in Ligue 1, but when at UCL and facing a team with good quality players, they play with pressure. the competition between each team in UCL will definitely be different when they compete in Ligue 1. This competition between teams that they may not get in the league. if Ligue 1 is more competitive, maybe PSG can also develop and start to get used to the pressure of the game like in UCL.