You could see it either way because you could also argue that Monza scored such a late equalizer. If you take the first 90 minutes it wasn't really a great performance by Juventus, but it was quite typical for them and how the game went. Yes in the end it always feels lucky when a team scores a goal in literally the last minute of the game. It ist even more exciting when the goal to tie the game happened just moments before the decisive goal then is scored.
The winning goal for Juventus was created very close to Monza's equalizer. This was certainly quite interesting and could be said to be quite lucky for Juventus because Juventus was able to win in the final minutes of the match, which was quite short time for Juventus. I was also surprised when Monza was able to create an equalizer in that minute so I thought the match would end in a draw, but Juventus were instead able to do something extraordinary on such a short opportunity.
Whatever you call that goal, whether it was lucky or not, the goal was crucial for them as the worst thing for Juventus now would be to fall behind Inter Milan too far too early. I think Inter has the strength to remain unbeaten for a long time, which does not mean that they won't miss out on points because of draws sometimes. But if a team wants to stay at eye-level with Inter, winning is a must in games like that against Monza. Juventus Turin delivered and they are keeping the league exciting.