Yes, the gap between Milan and Juventus is quite a lot from the teams at the top. It's just that for Serie A, the competition is very tight.
Indeed very tight as most of the top teams win their games nonstop or at least they don't lose them. Lazio has been doing amazing and so has Atalanta, Inter and Fiorentia, which is probably the biggest surprise of them all as I rather saw them further down the table.
I thought at first Lazio and Atalanta would not be as good and consistent as this until now in matchday 13, but it turned out to be wrong, and they continued their good performance in every match. Not only that, even the top scorer in Serie A turned out to be Atalanta's Mateo Retegui, with 12 goals. He is awesome. This proves that the clubs in Serie A cannot be as calm as before dominating the top standing, because if they miss 1 defeat, then their position will be immediately shifted by other clubs.
I agree because both teams aren't actually known for having long winning streaks, but this is not the case now. They both have impressive winning streaks and while teams like Juventus keep dropping points because of all the draws, Lazio and Atalanta took the lead against those other favorite teams. For the league it is great as that is what people want to see, tough competition throughout the season in a best case scenario. But I doubt that the first five will continue like this. It would be incredible, but someone will probably fall behind at some point.