It will still be a big challenge for PSG to perform well in the Champions League next season, because apart from PSG still having to get some of the best players, the PSG coach himself must also be able to bring better changes to the players at PSG so that PSG's strength is to compete in the League. Champions can increase even more because it's time for a team as big as PSG to get a title in the Champions League by beating teams that have been successful in the Champions League in previous seasons.
It's true that I agree with you, Luis Enrique has a tough job for that task which is to win the Champions League. Looking at their line-up, they should have won it last season, when Messi was still strengthening it. But the fact that the PSG squad doesn't have the mentality at the Champions League level is a fact. Enrique certainly understands that and that will be the priority work for next season.
But to reach the Champions League is not easy, Pep Guardiola was only able to achieve it last season after seven years of hunting him with Man City. If Enrique can do it quicker then his luck will outshine Pep, maybe just like Tuchel at Chelsea.