PSG's first mistake since a few seasons ago was that they tried to make Galacticos just like Madrid did in La Liga but in the end things like that don't really have a big impact on their performance in the Champions League especially when you see what they do by looking for old players like Messi or Sergio a few seasons ago that only fulfill the quota of star players but their age is not really suitable for big competitions.
Now Enrique is trying something new where they are focusing more on developing young players even though the initial transition did not match expectations but now the results are quite visible where some of their young players seem better in terms of performance for now.
Now they are trying their luck again even the chance for the semi-finals is still quite big for them now so of course this is a good moment as proof that indeed what Enrique did (although this is their first season changing the old system) but the results are still quite good.
You're right, PSG's biggest problem in recent years has been their attempt to build a "Galácticos" team, similar to what Real Madrid did in La Liga. However, relying on veteran stars has not yielded the expected results in the Champions League. It's clear that having a team full of famous names does not guarantee success in such a demanding tournament, especially when these players are no longer in their prime.
At least for now there is change even though it was initially considered a big risk because the changes made by Enrique really rely more on long-term trust and when the results do not match expectations then dismissal can be one of the possible things but in the end he was able to make the situation improve over time with the prospect of young players for the long term.
The current situation is not too much different from the previous season for PSG in terms of competition although at the beginning they were quite troubled and almost did not even qualify for the play offs but now they are on a really very good track and this quarter final they are the favorites although their opponents are also not easy opponents to beat because Aston Villa is a dark horse for now.
Interestingly, if in the end PSG can win over Aston Villa then indirectly they managed to beat 3 EPL clubs for the Champions League this time after they beat PSG in the league phase and Liverpool in the last 16.