I have doubts about getting to the final and winning the cup, and I'll explain why.
Napoli is working hard on the market and is looking for experienced players, but they have some weaknesses and in fact they have made some serious mistakes in some matches, such as against Como.
If you want to win European cups you can't make these mistakes
Your doubts are justified. The UCL competition is different from Serie A and Napoli level is still not enough to eliminate other strong candidates to reach the UCL final, but it does not mean it is impossible because there are still other factors such as luck. Another reason we know when Napoli won the Scudetto last season is that their performance is still not strong enough, there are still shortcomings in Conte squad, namely their goal productivity is quite low in Serie A, which indicates that their attack line is still problematic. I don't expect much from them in this competition.