I used to think he could develop in the DM role but I'm doubtful now. He's not exactly young either, he's 25 this year. Teenagers like Camavinga and Bellingham are already better players than him.
You don't need elite technical ability but you need willingness to show for the ball and positional sense. I thought he could replicate someone like Jordan Henderson who was a similarly energetic midfielder but adapted to play as a holding midfielder. He isn't showing it though. Sadly, Scott isn't even on Hendrson's level, and Henderson himself was dislodged from the holding role when Liverpool signed an actual, quality holding mid in Fabinho. Forget Busquets, McTominay is numerous levels below that.
He is what he is. He might be a decent partner for an elite defensive midfielder, but even that us no guarantee.