Ligue 1 teams are not that strong this season except PSG. However, teams such as Monaco, Marseille and Lille have battled PSG for the title in the past. But this season these teams are not strong enough. And their performances have been erratic at the start of the season. Apart from PSG, no other team has won three matches yet. However, Marseille, Lens and Monaco are still unbeaten. And the Lille team won two and lost against PSG.
In a first season with without-Mbappe-PSG, if other clubs in Ligue 1 can not beat PSG and take the trophy, they will need many more seasons to do this. Because it's a big change in PSG and if they waste this season, a next season PSG will adapt better to play without Mbappe and be able to continue their domination in France.
This season is a biggest chance for other French clubs to take advantage of this big player resource loss in PSG, to beat this giant and make Ligue 1 less boring after many years under PSG domination.
PSG's management is very rich so they can spend a lot of money and build a strong squad. No other team in Ligue 1 spends as much money and builds a strong squad as PSG. This is why we see PSG dominate every season. PSG easily won the Ligue 1 title.
They are rich but they have restrictions from financial law and their transfer strategy seems to be changed entirely in two latest summer transfer seasons. PSG no longer seriously chased star players with very high transfer costs and lucrative salary demand from players. They are still playing well in Ligue 1 but this strategic change obviously gives other clubs in France more chances to beat PSG.