what kind of results should they be getting then? they arent Lazio/inter level of team obviously, they have the 2nd best team in the league and they play together for a few years now. they finished with 86 pts last season (Roma finished with 87 pts, i guess they shouldnt get those results either), naturally they would be improving the following year with Serie A as their only true goal to focus on.
Juve plays bad :

:, OK. somehow we still scored more goals than Napoli, guess its all individual brilliance.
Milik was never a key player for Napoli hence his injury dont bother them one bit. scoring regularly? Lazio scored more than them as well btw, and they have a worse attack.