They transferred important players and paid high transfer fees. The only reward for the money they pay is the expectation of success. If PSG can achieve success, Enrique can stay at the head of the team for a long time. In my opinion, Enrique should be able to make it to at least the quarter-finals of the Champions League.
Unlike you, I'm not sure at all about Enrique being successful in PSG. In fact, PSG had many superstar players in the last season they could help the team like Messi but they didn't have a good coach like Enrique in his team, Now when some players left PSG for the other teams, Enrique started working there but still I don't think if Enrique is enough to help PSG improve the team.
I think PSG still can't earn achievements in the Champions League.
I personally appreciate Enrique's talent. Before he arrived, PSG was a mess. There's so much going on with PSG. Enrique came and rearranged the squad. In addition, many star players have left and been replaced by young rookies. Up to now, the team is entering a stable phase. PSG rose to the top of the group of death with 6 points after 3 matches. This shows that Enrique has been successful as a PSG coach.
It is difficult for PSG to enter the quarterfinals. Actually, they need to be more robust to compete with big teams. They must make further breakthroughs.