It is not simple to give this kind of games meaning to be honest. On the one hand you see big clubs fail against those teams because they don't go all out and believe that they can win the game easily when they perform at 80%. On the other hand I recall that Bayern Munich was defeated by a team that was playing several classes below them in Germany. It wasn't even 2. Bundesliga I think and yet Bayern Munich lost the game. So it was a good job by PSG to approach this game with high focus and intent to win it, but simultaneously nothing of importance really happened here.
Surprising things sometimes happen in every football match, sometimes big teams underestimate small teams until finally the small team is able to perform impressively to beat the big team, and this was done by PSG even though the opponent looked weaker. But PSG remained focused on the match and continued to field their main squad so that it would be easier for PSG to win, and it's true that it was very easy for PSG to break through the opponent's defense and their team seemed to be feasting on goals, but this was very risky because they were worried that the PSG squad would suffer injuries, but luckily in this match the PSG players were good. It's good that this is also a way to hone the players' skills before facing matches in the 2nd round of this season.
They fielded their main squad and made sure that this game is over by halftime. In my opinion that is the only right thing to do in these matches. Of course coaches can decide to give other players a chance. Perhaps young players need more practice or players that don't get their chance to prove themselves very often, but sometimes they exaggerate and field 8 new players. The whole team then doesn't know each other, the opponent gets lucky out of a sudden and the favorite is down 0-1 and the clock is running. That should be avoided and PSG had no mercy and did their best to have a relaxed second half of the game.