Napoli not necessarily stuck. They play two different positions, wing forward and Central forward. So if PSG wants they can buy both.
And there's worse outcomes then being stuck with world class Osimhen instead of signing mediocre Lukaku.
I can't imagine PSG will sign both Lookman and Osimhen, I think it will really fall down to where the likes of Kolo Muani now fit tactically.
On paper Osimhen is a superior player to Lukaku yes, but at the same time napoli can't sustain his massive wage and expect to unlock their mercato which is still very much incomplete and reliant on the sale of Osimhen.
Realistically Osimhen is hardly drawing a bidding war due to the excessive costs involved, seemingly only Chelsea and PSG are remotely serious about him, the former being far less appealing proposition than PSG.