Isn't he a CDM these days?
He is. Mainly because our squad wasn't balanced last season and we only had Verratti as a defensive midfielder. He has adapted there and is used in this position to give cover to our defence because our forwards, especially Mbappé, aren't the best at tracking back and defending and our full backs are terrible.
However, there is also the fact that the Marquinhos-Thiago Silva pairing isn't that good. They are worse than the sum of the two players. Thiago Silva is indeed the only world class CB in this team and Marquinhos suffers a lot against physical forwards. This is what prompted Kimpembe to become a starter (he is a physical beast and like the duel) while he is prone to terrible mistakes.
I don't really know if he will go back to CB when Thiago Silva leaves (he is out of contract in the summer and the club has still not sent any proposition despite his loud wish to stay at the club) since it might be important for his future in national team. And i don't really know if he should keep playing as a CDM if we actually buy talented midfielders (we want Tonali and are interested in Camavinga).
He is still a better CB than the guys we bought recently though : Kehrer and Diallo.
I like the guy and i like the fact he is very attached to the club but i really don't see a future world class player in him. Just a good player.