I think in the Champions League Napoli has all the chances to make it to the next round. The only reason I am saying this is because Barcelona has the same issues and are so much worse than they normally play. They did play against each other in the Europa League in 2022 and those two games ended 4-2 and 1-1 for Barcelona. But this time I think Barcelona is even worse. If Napoli plays a good first leg at home, everything is possible.
Napoli were strong in the last season but they no longer maintain it in this season. They have enough good players to compete fairly and equally with Barcelona but chances for Napoli is not too big. It is just like 50/50 chance for them to beat Barcelona at the end in an aggregated result.
If attacking players of Napoli like Kravatskhelia, Osimhen have excellent matches or just some magnificent moments, they can win over Barcelona. Generally they don't usually have such good performances in this season so suddenly have such in two important matches will be big surprise from Napoli.
You said their chances are not too big but estimate their chances could be 50/50. Doesn't sound like a bad deal to me as being at 50/50 against Barcelona is ok.
That's the crux of the matter, the players still possess enough quality to compete in the league, but now everyone believes it is all about Spalletti who left the club. But the players also have responsibility. It can't be just the coach and that's it. Because they played worse when Spalletti was still there last season and that is often forgotten.