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.
I agree with your opinion that Ligue 1 is one of the weakest leagues among the top European leagues. In fact, we can see how dominant PSG is in Ligue 1 and how other teams are unable to compete with them. This is different from other top leagues such as La Liga, Premier League, Serie A or even the Bundesliga which have rivalries in competition. But I think PSG is not a weak team when compared to teams from other leagues. PSG dominates Ligue 1 because other teams are weaker than them, but I see PSG can also become one of the best teams in European competition. PSG made it to the semifinals in the UCL and that shows their level. It's just that they have never been among the favorites to win the UCL in my opinion.