I can see that it may not be as easy as winning ligue one of course, but it shouldn't be this hard neither. They have been trying for the last 5 or so years to win it, and they have spent so much money and got so many great players and none of that helped them, they always lost.
I think it's quite important to realize that while it's hard to win UCL title, when you spend this much money on it, it becomes something more possible, this is why we should be considering the situation they are in right now as not normal. I believe if I built a team with that much money then I would definitely expect them to make it better, I would expect them to have at least one UCL trophy by now. Considering they have good players, I assume managers were the main problem.
IMO, what is actually the problem with Paris Saint-Germain is Nasser Al-Khelaifi and his sporting director. yeah, they can't do as well as Manchester City. at least, City is led by a competent coach. also, given the freedom to have players he likes in his squad. ideally, a coach knows which players they need to make their team stronger. different from PSG, several previous coaches were not very competent in handling a team as big as Paris Saint-Germain. Plus, the selection of players is under the constraints of club management. yeah, like when PSG was managed by Galtier. apart from having just managed a team as big as Paris Saint-Germain, he also doesn't have much experience in the international arena. the most crucial thing is, Galtier cannot control the conditions in his own squad's dressing room.
Finally, there are many rumors of disputes occurring within the PSG team. What's worse, Galtier only carried out his duties according to the instructions of Nasser Al-Khelaifi or the club management. That's also why PSG always fails to win the Champions League trophy. When PSG was filled with the MNM trio, this team was sharp in the front line but not in the midfield and defense sectors. PSG is just wasting money, even though they are under a competent coach. It is possible that the French League giants can win the Champions League trophy.
Now Paris Saint-Germain is managed by a coach who is quite experienced, especially in the Champions League. but still PSG is not yet the ideal team. next season, if Enrique stays with this team. There will be changes taking place, especially in the midfield and defense sectors. especially, if in the end Mbappe leaves. that means, Enrique will look for the ideal candidate. For Ligue 1, as we can see, it seems that this season their progress in defending their league title will not encounter any significant obstacles.