I'm not too familiar with Tchouameni, so I can't comment much. However, I do remember watching him in the Nations League final against Spain, in which he lined up next to Pogba in a 3412 formation. Like yourself, I didn't find him anything special defensively. Actually, I remember being impressed with Pogba's defensive work more than Tchouameni's, which is saying something really.
Now, I personally don't think we need a out and out holding midfielder. I just think we need two box to box midfielders who are defensively sound, especially if we continue with a double pivot (hence the love for Fred and McTominay). I guess Tchouameni would fall into that category.
We have; however, been recently linked to another defence minded midfielder in Boubacar Kamara. Again, not a player I'm familiar with, but could be a stop gap to rotate with McFred, whilst focusing on a Matic replacement in the summer.