Osimhen was an option for PSG even in the last season. I think Osimhen could have even better performance in the last season when he was in the better form but now PSG knows they can't expect to see a miracle from this player but he can have a good performance like two years ago and he can be out of the good form like last season. I think there can be better options for PSG than Osimhen and they should not be worried and run for finding a replacement for Mbappe because Osimhen and Mbappe are not at the same level at all.
Your comparison isn't sounding solid, I know I'm the last season, towards the end of the league osimhen's performance did dropped and that too has affected his price but on a second taught it's possible there were factors that led to that which if taken care of he would do better, at PSG those factors that led to his poor performance may not be there but PSG still isn't a fit for him, his career may not do so well in PSG.
At the moment PSG isn't prioritizing getting him into the squad and he is yet to even show any interest in PSG as an option for his move, there were rumors of an interest in him by PSG last season before the end of the season but the deal didn't pull through and even now it's not looking like one that they would want to revisit again. Away from PSg, in other teams if osimhen gets and opportunity he's still gat some good potential.
I'm even surprised to see that many people are judging Victor Osimhen with his performance of last season with Napoli hence their opinion that he's unlikely to deliver great performances should a club like Paris Saint Germaine sign him. I think the whole of the Napoli team last season was just short of their best and that affected the team's performance which was why we didn't see Victor Osimhen score the same incredible numbers we saw him score last two season. At Paris Saint Germaine, I strongly believe that Victor Osimhen will do exceptionally well because the team already have quality players that'll help supply him the crosses and passes to convert. There's no doubt that the Nigeria international is a very prolific striker that can succeed in any of the top clubs in Europe because he's actually proven how good he is.
Just like you said, Paris Saint Germaine aren't currently doing much to land Victor Osimhen to their club and we've seen any statement from Osimhen that suggests his desire to play for Paris Saint Germaine. The transfer window still have one more month before it closes so let's keep our fingers crossed and see what the future holds for Osimhen