I agree with you, Messi has contributed with Goals and Assists to lead PSG to win the title in the domestic competition, but he was unable to carry PSG to win the UCL trophy because they are still unable to compete with other top clubs. At that time, PSG front line was filled with the world's best players, Messi, Neymar and Mbappe, while in other positions PSG also had classy players, so all players had the same responsibility. Psychological problems can affect his performance, but as a professional player he has done his best for the team he plays for.
Messi was not the player he used to be when he left Barcelona for PSG. Would I saw that he failed to gain his rhythm because he was used to the pattern of play of his former club? Barca had some of the best players that helped the Argentine shine in Spain.
A tree cannot make a forest, therefore saying that he didn't contribute much to the club is unfair. He did all he could because they won League One but failed to make an impact in the UCL. The failure of the reign of the super attacking duo of Mbappe, Neymar, and Messi was challenged by their inability to put aside personal ambition for the club's glory.