Differences in quality and perspective of club management and applicable rules so as to give birth to a different vision. If I am not mistaken, PSG has just been built more coordinated after they have a new owner and he starts targeting the Champions League as the biggest achievement. In contrast to Bayern Munich and even there they have to make the rules at least German players must be more than outside players. Bayern Munich has become one of the best clubs when playing in the Champions League while the PSG level hasn't to that yet.
Compare PSG with Bayern Munich is not good and I see a better comparison is between PSG and Manchester City. They are both new rich clubs last decade and they both spent a lot of money for transfers recent years. However, their strategies are different and Manchester City changed by signing with Pep Guardiola and adjusted their transfer strategy after that. PSG did not change anything and we can see Manchester City got first success in Champions League last season while PSG are still struggling to have a second Champions League final.
So that the project being worked on by Luis Enrique will be far more difficult where they have to build the squad to be stronger and take time so that PSG is able to compete in the Champion League. If Luis Enrique is able to build the club level to be stronger then I am sure they will achieve success as did Pep Guardiola in Manchester City.
They signed with Enrique with belief that the coach with his experience in Champions League, will be able to help them to win Champions League. This season is last chance for PSG to win Champions League with Mbape in their squad. They player is ready to move to Real Madrid in the summer but PSG actually prepared for it by stop buying super star players but focus more on star players who are young and still ambitious to win titles.