I agree with you, since only PSG is the strongest, they will feel relaxed in improving the team continuously. This is because they know that they will always win their league come no matter how poor their performance is. This is the major problem, why they cannot compete the other title champions. In fact, I will say that Ligue one is a weak league, because among weak clubs, there will be a strong one.
That's right bro, because PSG is a team that has strong stamina and a strong team, but all of that can be weakened because in Ligue 1 they don't have comparable opponents so that PSG can reach first place in Ligue 1, they will feel weak when they enter the Champions League with even stronger opponents so they can improve themselves to be even stronger when they feel that strong opponents exceed the strength of the team they have, it's true, as you said, Ligue 1 can be said to be a strong league. because PSG was able to get first place by beating weak opponents so that every year when Ligue 1 started they easily always finished in first place like they are now.