Saying they have a second best team is like saying Europa League is the second strongest European competition. Technically true, but it doesn't show it is miles behind Champions League, just like Napoli is behind Juve. And somehow they are ahead.
Player by player, they are not that much better than Roma, Inter and even Lazio. Yet they are 14 points ahead of them.
As you said, looking at points only, they are better than Bayern. But I guess that is "natural improvement" for you.
If they do not sell anyone, what do you expect of them next season. A perfect score?
Looking at the individual quality in this team, play itself is actually real bad, especially when considering the typical Serie A opponents.
Nice cherry picking there. Lazio also conceded more than twice as many. Probably because Napoli have such world class defenders and absolutely nothing to do with coach.