For a few seasons PSG performed well, among the other teams there was no team that had a chance of winning the title, perhaps they have not been very successful in the last 20 years. The 3rd and 4th teams in the Champions League will be easy opponents for other teams
The French League is absolutely nothing compared to other standard league with fierce competitive race amongst themselves. Ligue One have only entertaining features but when it comes to the real deal, they snapped out of it because they're incompetent to face major clubs. For instance, in the UEFA Champions League, we all know what always happen to Paris Saint-Germain failed attempts in numerous times. They've tried and tried until they get no hope left. Perhaps it doesn't mean they will give up but continue to make attempts because winning is sure.
It is recorded that the only League 1 club that won the UCL title was Marseille, but that was a long time ago, even PSG, who dominated League 1 for years, have not been able to achieve results like Marseille