The number of title hopefuls in Serie A this season is much higher, with the competition for the title increasing. I don't think a team like Juventus or Roma can win the title in this situation. Juventus are now 11 points behind Napoli. If they want to get on the track fighting for the title, they have to win at least the next 10 matches. At least I think so.
Yes, you're right - if you look at this question from a statistical point of view, then teams like Roma or Juventus have already "used up" (almost completely) their limit on unsuccessful matches for the whole season. And now, in order to become the champion, they have to show a phenomenal winning streak, is it realistic given the level of play that they show and with that strong competition from other clubs? I strongly doubt it.