I don't entirely agree that PSG is too strong for Ligue 1, they still have competitive teams like Monaco, Lille, Marseille and Lyon. While PSG’s financial strength and star studded squad makes them stronger, historically teams like Monaco and Lille have managed to win the league despite of PSG dominance.
PSG inability to replicate their success in Ligue 1 in the champions league is clear. Despite the signing of world class players they have constantly fallen short in the biggest stage. For them to improve they should be able to prioritize developing young players to understand the club’s identity and also a coach with the right mentality to propel them to perform better in the biggest stage.
I just want to admit that PSG is indeed a strong team in Ligue 1 and indeed, sometimes PSG can also get draws and also lose against mediocre teams in Ligue 1. But anyway, the fact is that PSG will remain firmly at the top of the Ligue 1 standings and also, although there are still teams that have a great history of winning trophies in the past. But still, the reality in this era PSG remains a better team than the other teams you mentioned.
I also admit, there are still teams like Lille who also managed to beat Real Madrid and Atletico in the Champions League and also managed to hold Juventus to a draw. But anyway, the fact is that Lille is also only in fourth place in the Ligue 1 standings, and has a 10-point gap with PSG at the top of the standings. So evidently, PSG is indeed too strong in Ligue 1 and if we compare the competition that occurs in Serie A, of course there are many teams that are able to be at the top of the table, unlike in Ligue 1 which can always be ascertained PSG will always be able to finish at the top of the table.