I'm worried that if Napoli buys Lukaku, it won't match Napoli's expectations, and won't even have any impact on the team. In my opinion, it's much better to look for younger players whose stamina isn't a priority. If they force it, the big possibility is that Napoli will of course waste money on transfers. that happened, keeping Osimhen rather than having to sacrifice him just for an old player like Lukaku.
It seems like what you are saying makes much more sense than throwing away Osimhen who then brought Lukaku to Napoli because a player like Osimhen can still be relied on as the best spearhead in the team. Meanwhile, Lukaku still cannot be relied on as the best spearhead in the Napoli team, so it would be a good idea for Napoli not to throw away Osimhen for a player who is no longer young like Lukaku. But if Napoli can bring in Lukaku without throwing away Osimhen it would also be better because a team that has some of the best front line players will be much better although other players in the line also need to be considered.