I'm hoping Kean is similar to the Adama Traore situation. The kid went from Barca to Villa to Boro. Had terrifying pace and strength but was so, so raw. Always picked the wrong final ball or tried to do the same thing everytime at Boro, positional sense was atrocious. Pulis always swapped him to the other wing at half time, purely to keep him close to the dugout side as he constantly had to tell him where to stand, where to run etc.
With coaching, perseverance and maturity on his part, he's gone on to significantly improve and become a sought after asset.
For me, it's much too early to write Kean off. The only factor in that should be if Kean wants to leave... Even that for me, would be better on loan, for now.