PSG may dominate most of the time, but keep in mind that even bottom clubs of Ligue 1 can make a difference of the title race-a scene perhaps not as frequent in other "big" leagues. Now with Messi, Neymar and Mbappe and Ramos the only thing missing is a strong stable opponent in the league, like Bayern has with Dortmund for example. Someone who at least challenges it year in year out. The problem is Lille Marseille Lyon etc, they perform one season and the next theatre out the window , sometimes not even getting into European competitions.
Exactly. There are no consistent team in this league except PSG. This is mostly because the remaining teams don't have a very solid squad like PSG as they are not as rich as PSG. However, the other teams you mentioned can't even be consistent about finishing at top positions in the standings. They are generally ending seasons being far away from the leader in terms of points.