I still think he's weak with not so good balls he has to send to spikers other than Hinata.
He could also organise the attack better when he's the one defending
He has to be better at blocking and the follow-up too.
Training with national level contenders, equipement and national level coaching staff will probably help him better all of his weaknesses, and strengthen his core qualities. And also broaden his ability to adapt to any spiker.