I've said plenty of positives already, so please don't take this the wrong way.
But I thought it was worth mentioning that at times we were hoofing it up the field far too much, and when we did that, we conceded possession every time and went back to defending again. Napoli pressed us better than any team I've seen this season, cutting off angles and putting our defenders under immense pressure. Delph in particular ended up passing it back to Ederson pretty often.
We need to really work on keeping our composure and not resorting to hoofing it. We just do not have the midfield or strikers to win the ball if it's hoofed forward.
That said, I don't think any PL side this season will press us as well as Napoli did. The danger for any side trying to do this is of course once we've beaten the press, we've taken 3 or 4 or 5 opposition players right out of the game and we can attack them at speed.