Remember, even the very best fullbacks in world football look shaky at times against great attackers. That's just a fact of modern football. Robertson, TAA, Kyle Walker. All can be got at defensively. Look at that CL semi between Bayern and Barca. Some of the world's best fullbacks on display and both teams were wide fucking open in the wide defensive areas.
So any opposition fans saying Chilwell is a joke defensively can pipe down. He's average defensively just like every class fullback.