It's the biggest problem in the team at the moment aside from the manager. The issue is our midfield options are fundamentally limited - we have no one who can both shield our defense and distribute the ball from deep. Here's how I'd break it down in terms of our central midfield options:
Kante - not a DM and never has been. He can be crowbarred into that role but the tradeoff is that our buildup suffers immensely. Against Arsenal, they just stood off of Kante and Zouma and only pressed Silva. Kante was totally incapable of taking advantage of the space and time afforded him, and against any team that sits deep he isn't a real option. He's also a terrible option as an 8 - he's very poor at receiving the ball with his back to goal. Needs to play in a midfield 2 with a reliable defensive midfielder who can sit deep and move the ball quickly to make up for his deficiencies - it's not a coincidence that his best periods have come alongside players like Matic or Drinkwater (when he was good) or Pogba.
Jorginho - good at distributing from deep but an utter liability defensively. Will be rendered useless by any lateral or vertical movement from any opposing attacking midfielder. Also surprisingly vulnerable to pressing and is liable to give the ball away in dangerous positions when pressed. Needs to play in a different league where pressing is less prevalent.
Kovacic - absolutely brilliant dribbler and a tidy passer, but his value is hugely curtailed if he can't dribble forwards. He's also very poor with his back to goal, so a role as an 8 is unsuitable. Basically he needs to play as the more attacking member of a pivot alongside a deep-lying defensive midfielder, so he has license to carry the ball forward and receive the ball facing the opposition goal.
Mount - our best midfielder and player this season by a distance. He is best used as an 8 but can be the more attacking of a midfield 2 in a pinch. Better in a 3 though.
Havertz - can only play as an 8 or a 10. Throwing him in as an 8 where he has more defensive responsibility was probably a mistake this year; he's struggled with the physicality of the league and exposing him to more of that was wrong. His best performances have come as a 10, so a midfield 2 behind him is required.
Thus you can see we've assembled a collection of players who can't actually play together. The most obvious missing piece is a defensive midfielder who can break up play and distribute - hence our documented interest in Declan Rice. Personally, I'd have sold Kante last summer if there was a suitable offer; he's not the easiest player to fit into a side all things considered, especially at this point in his career.
The one player I'd try to incorporate more is Billy Gilmour - he's a brilliant passer from deep areas and he's at least defensively diligent, far more so than Jorginho. I feel like Gilmour / Kante could be a functional midfield pairing, or a midfield three of Mount / Gilmour / Havertz might work. Obviously it'd depend on the overall selection as well.