Stefano pioli is a good coach, but I think considering AC Milan's bad position right now in the Italian league, they need someone with a higher and better pedigree. AC Milan have lost their place among the Italian elite and need to do something quick to regain it.

Milan should have gone for a coach such as Jose Mourinho, he has in the past being a champion in the Italian league, and I believe he'll bring them out of the slump, but I do not know if he'll be willing to coach AC Milan.
Anyways I wish Pioli luck, good luck!