PSG is always in doubt when appearing in the UCL so they are not favorites to win the UCL title because PSG has difficulty competing with the top teams there, PSG always dominates League 1 and always competes in the UCL but still they can't do much in the UCL they always get knocked out before reaching the final, even though PSG have good players but not enough to prove their strength in the UCL.
The match between PSG and Barcelona was really awesome to watch. PSG had a new coach like Enrique to help this team have a better performance in the Champions League and they didn't have their superstar players like Neymar and Messi but Barcelona was recently had a better performance after they won the game against Napoli.
As you said PSG was always unstable in the Champions League and that's not something new to say Enrique is guilty of this loss but they should try much harder to beat Barcelona if they want to remain in the tournament However this can't be easy for them all after the 3-2 lose they had.
Indeed, Enrique has worked hard quite well considering that currently PSG can still maintain its position as the top of the Ligue 1 standings and also as the strongest team in French football, plus they managed to reach the quarter-finals of the UCL.
But the defeat few days ago against Barcelona made everyone disappointed and of course Enrique was quite regretful about the defeat because after all, the first leg of the home match was big opportunity for PSG to win.
For the next match, it is clear that PSG will have difficulty winning because in the second leg they will play away from home, Barcelona will definitely do their best in their home match and this will put pressure on PSG.
But it seems that PSG doesn't have the mentality of being UCL champions and they will definitely be eliminated in the quarter-finals.
They have lot to learn and PSG is only guaranteed to win Ligue 1, next season it is certain that PSG will be even more difficult because of the departure of their best player Mbappe.