What you are pointing at regarding Lukaku in an important thing to be considered because a point is not enough for them to sit on the top of the table, among the top fivein the table Napoli are the only one with a less goals, this alone show that they can't hold that place for a long time if they don't have a very strong striker that can give them more goals, I like Lukaku but I think he is not in the right position to lead the team, he's old and they shouldn't depend on him to do all the work, losing against atalanta with almost 3 goals was a total disgrace because it clear that even their defence line are also having issues not only the strikers and if this can't be fix then the will lose the top.
To be fair, Napoli plays a huge defensive scheme with Conte, which was known before the season started, we knew that is how they are going to play. While it's true that last two games were bad, I am pretty sure that they are going to end up getting better results. This doesn't mean that I believe Napoli will win the league, of course they could lose, but that doesn't mean we are going to end up with something that would profit us, that is not going to happen.
We need to make sure that things aren't always that great, and because of that we need to make sure that we are dealing with a better result one way or another, and Napoli can't keep losing points every game. They did that already, and they aren't suddenly a terrible team neither, so that means they will keep winning some games.
Also, they are followed by Atalanta and Fiorentina, which nobody expects to keep going like this, I bet that they are going to have some losses and bad games, they are on a winning streak and they are expected to lose. Atalanta would be a shocking result while also not be a shocking result, they won Europa last season, so they are expected to do well, not sure if they are expected to do well enough to win the league though.