In my opinion, the French League is one of the weakest leagues among the European leagues. The quality of football in this league is not very high, the players and teams are below the Champions League level.
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.
A reasonable reason, because when talking about Ligue 1 in this era, then of course anyone will agree that PSG is the best. Although indeed, in the past Ligue 1 at least had Marseille which also managed to have a good history in the Champions League,because Marseille had won the Champions League trophy in the past. But in this era, even though PSG has made great efforts by buying great players, but PSG still failed in the Champions League.
What's worse, the other teams in Ligue 1 are unable to put up a strong fight against PSG in the race for the Ligue 1 trophy. Thus, even though PSG is the best team in Ligue 1, but in reality PSG is still veryweak if PSG are in difficult competition with teams that have another great level in the Champions League. So yes,it's not wrong if you say that Ligue 1 is the weakest league compared to other big leagues in Europe.