The draw against Napoli is quite natural, especially since Inter Milan is in a slightly slumped mentality after being eliminated from UCL, but I think no one doubts Inter Milan to win the Scudetto this season, they are already very far ahead in points from their rivals and also in terms of the quality of the Inter Milan team. This season is very strong so it is not difficult for them to recover, losing a few more matches in the continuation of Serie A matches this season I think will not have a significant impact on them because it is very likely that Inter Milan will ensure the Scudetto this season.
Napoli is not a mediocre club. Don't forget that they are the defending champions and still have lots of quality players. I guess Inter Milan will be comfortable with the one point they got in the game because Napoli could have also won the game. For now, Inter Milan has little completion that will stop them from winning the league because fourteen points is not easy to lose. It was a great disappointment for them to be knocked out of the Championship League because I thought they would have at least gotten to the semi-finals. They would have to wait until next season to see if they can replicate last season's performance when they made it to the UCL finals.
Napoli without doubt are the reigning champions of Italy and shouldn't be considered a mediocre club but the truth is that they've not been consistent and impressive as they were last season which have resulted to the club's management decision to part ways with two coaches already as the club is currently with their third manager of the season.
That being said, I think Napoli will be very much okay with their result against Inter Milan in their last game in the league because very few teams have been able to get a point while playing away at Inter Milan since the start of the season. Napoli are trying to make sure they finish the season in the top four of the league table which tli think will be very difficult for them as a club because other teams in league who happens to be ahead of them at the moment also wants to make it to the top four before the end of the season.