The reason for PSG they spend lots of money but they can't get anything in the champions league is mostly because they didn't have a good manager and they just bought superstar players while PSG didn't have a balanced team, this situation made chaos in PSG that's why they players couldn't have a good atmosphere in the team to have good performance.
This can be one of the reasons that makes sense actually because looking at the current condition of PSG they don't seem to have a condition that can be proud of in terms of their management which makes the money they spend seem to be useless.
Even though we know that the Champions League is not a place that anyone can enter but should be with PSG's finances they can talk more than now.
They always focus on ready-made players is also one of their tendencies to struggle a little because they always buy old machines like Ramos or Messi, which even though their names are unquestionable but their qualifications are clearly reduced due to age.
In addition, when the competition factor is also lacking in the domestic league, I think this makes their conditions more difficult when they are in tough competitions because if you look at other competitions such as La Liga or EPL it can be said that the competition in Ligue 1 is much easier which makes them accustomed to competitions that are not too difficult to make them fail to adapt to high competitions such as the Champions League.