The main problem for PSG to not getting good results in the past was mostly because of the unbalanced team they had, PSG had the best forwards however there was a negative atmosphere in the teams but they had the best forwards and they didn't get good results because in the other positions, and especially in the defensive line they didn't have good player, I think this teams still don't have good defender and you can see this problem when they are going to play in the Champions League against strongest teams.
Although PSG bought quality players, they could not keep the atmosphere in the dressing room normal. PSG's dressing room was always hot. In the beginning, Neymar and Mbappe had a good relationship, but later on, a lot of distance between the two stars developed. Then when Messi was brought into the team, Mbappe created a distance with Messi as a result of which bad results in the performance of the field were a regular occurrence. The club suffered due to poor relations between the players. Despite investing so much money behind the players, their achievements were meager. PSG failed there before they should have normalized the situation in the dressing room before investing so much money behind the players.