He's not done yet. He needs to improve his boxing skills. Fury survived the K.O. in this fight because he moved his head a lot to avoid being hit while Wilder was easy to hit throughout the fight.
His accuracy is there. Its always been there. What has made Wilder who he was is speed, power, and pin point accuracy. It has bailed him out on all his wins. What screwed him up in this fight was giving up speed for muscle. Power was still there but without that speed he couldn't get that accurate punch out. If he waned to add weight make it water or some fat. Bulking up with muscle is a horrible plan for a guy with his nature gift and bellow average boxing skill.
He's 36, ain't he? He's not improving anything. That ship has sailed. Hang them up for christ's sake.
Wilder was stumbled througjout the fight whenever Fury hit him. If you have a glass chin then you need to improve your defense. At least, you need to move your head to avoid being hit sometimes and do not stick your chin out like that.