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.
Comparing the league 1 with the other big leagues is not really fair to me because still takes a lot of time to be a big league and in fact it's all in PSG's possession that brings star players to attract football fans and boost financial traffic. But the way the PSG is doing it is actually wrong to bring the star players because the team cannot be recognized if it can't score a good young player. And in this case the other team in the league 1 is not even able to follow a team from the league to be able to score a talented young player from the academy so that it can be known with a popular team and have a good reputation and also can compete with other top teams.
And with regard to the PSG being able to compete at UCL, it's actually all thanks to star players like Mbappe who helped the team fight to the semi-finals. In the next season we can see how far PSG can compete in UCL without star players and I don't doubt PSG but this is a fact.