Nah not writing him off as a footballer. In fact in the right system he'll do well, that being a system which can accommdate a penalty box striker where loads of other players around do the leg work.
The problem is that he is the completely wrong option for a deep lying hoofball system that is over reliant on an athletic channel running striker to both hold the ball and stretch the defence. I think Calvert-Lewin is the best striker suited to the system, albeit he is definitely not the best striker we have. Tosun may well be the best striker we have but is not suited at all to the archaic tactics.