I think the problem with Romagnoli started when he was given the captaincy. He was still not ready for the change in mentality. Its hard to lead a group when you are not confident of your own abilities and there's a difference between knowing what you can do and actually performing it.
Because Romagnoli is actually a good player, let's not act like we weren't excited when he first joined us, and for the most part he looked like the real deal.
But when he became captain he lost focus, he thought he should argue with the ref and he began to make lazy and silly fouls. He is a much different defender today than when he first joined.
If it were up to me I would talk to him sensibly and tell him that we are giving the captaincy to someone else and that doing so would be for his own good. We want him to redevelop and we should pair him with an excellent defender who can teach him. I really wanted Thiago Silva, only to continue this passage of Milanese defence through the generations.
The banter era really fucked us because we lost that link between champions and developing players.