You are right. If they take it serious or not, PSG will definitely win the league. They have only played one match and people ha ve started complaining about their performance. This shouldn't be the case because if you observe the match, it looks like the coach doesn't want to stress the players yet. Three points were achieved which was Luis Enrique target.
You are right. Luis Enrique does not want to put pressure on his players right now. PSG has earned 3 points, that is enough. And we have seen Luis Enrique keep the experienced players of his squad on the bench in the first half. He brought Dembele, Hakimi, Doue and Mendes on the field after 61 minutes. We saw Kvaratskhelia on the field after 78 minutes.
Enrique is not taking Ligue 1 matches seriously now. This shows that Luis Enrique is already preparing to do well in the Champions League. Luis Enrique does not want important players of his squad to face injuries. That is why he has rested them.
Basically, winning the Ligue 1 title is not a big challenge for PSG. Even if PSG plays with their second-tier squad, I think they will be able to win this title. So both Luis Enrique and PSG players are not taking any pressure at the moment