Yes he's not Frenkie de Jong, but you'd be hard pressed to find many available options who fall into that mould. Lavia is incredibly press resistant and very tidy with his passing. He may not engage in many dribbles but from watching him you can see he's got all the tools to be an elite ball carrier. Incredible balance, composure, sharpness of turn at only 19. As he gets older and more confident, his ball carrying game should grow exponentially. You're also underselling Casemiro's progressive passing from midfield and I think combined with skills Lavia has, they would dovetail very nicely. Also, it would allow us to move Eriksen further forward into the final third, which is the best part of the pitch for him or be a backup for Bruno, allowing us to rotate more. Even if you think Lavia cannot partner Casemiro, I'd still prefer him over the likes of Fred and McTominay.
Also, Lavia is not ready to play as a sole CDM. He's got way too many holes defensively to fulfil that role and he may not even in future. What he needs is the right coaching and time to eventually develop into becoming an elite single pivot. If we threw him in there now, he'd sink in my opinion.