This argument, again, is one I don’t understand. You might be right. But Tosun has shown himself to be ineffective and a liability at the level Lukaku excelled at.
Lukaku will excel as a goalscorer at every level he plays at.
That doesn't mean he excels as a footballer.
That's the point - pretty much the only point - I ever make about him. He's a liability to a team, except for goals. That liability is less when you drop down the leagues in quality, which is why he failed at United and is now doing alright at Inter.