All the teams in the French league other than PSG are strengthening their teams just to perform well against teams other than PSG. There is no doubt that PSG can perform badly this season. PSG will be at the top of the points table with a big difference like in the past seasons, but there may be a tough competition between the teams from the second to the last position of the points table and the position of those teams may change. I always consider PSG to be the best team in the French league but they showed excellent performance last season so now their strength has increased so it is a dream for any team in the local league to beat this team. If it is the case that PSG ends the season undefeated, then I will not be surprised at all.
The difference in quality is so stark that it's no surprise that it's happening.
The French League teams are solely focused on the performance of their closest rivals, and I'm sure they won't put PSG in the same position as their rivals. That's realistic, and those teams only want second or third place to qualify for the Champions League. Meanwhile, PSG remains under no pressure to defend their title, allowing them to focus on the Champions League again, as they did last season.