This situation can be viewed from a different point of view - not having competitors and knowing for sure that in the end they will get the championship PSG can play relaxed and "for their own pleasure." This is very different from the situation in other championships where teams are always under psychological pressure and fear of losing points in some match. PSG may lose a lot of points but still remain in first place - after a third of the championship, their advantage over their closest pursuer is as much as 10 points.
They can't really play "on their own pleasure" because they are still seen as the dominant league winners who will win by a large margin every single game. The moment they have a tie or lose to a team, ANY team they will be seen as playing horribly for that game and there will be complaints from fans, bad things said about managers, talks about players not caring and all that until they win again.
I would rather play in Lille right now then play for PSG. They are doing badly this season but at least they got a win last year and that's all it takes to make the fans happy. They could suck as much as they want this year and fans will be just as happy because they already got their win and that's enough. PSG on the other hand was humiliated because they lost one, I mean imagine winning the league 153423 times in a row and just because one season someone else won, suddenly everyone attacks you.
But if we take it even more globally, for each individual player the situation does not differ at all in whatever club he plays - he must always play well because failures will bring him under fire. The pressure here is strong both on Ronaldo, who must live up to his star status, and on average players who must try to do their job. Therefore, in this sense, the pressure is the same and this factor can be discarded.
Now, comparing the situation of PSG and any English team that is fighting for the championship, we can hardly say that PSG has the same difficult situation, right? They can lose 3, 5 or even 7 points and still be the leaders. Yes, they will be criticized but they will have the title. But the conditional Liverpool, having lost 7 points, will not just fly out of the championship contenders, but possibly lose their place in the Champions League. I think the pressure on Liverpool and the criticism will be much tougher in this case.