But if you go by the lore, if you hit it hard enough and fast enough you can toughen it till it shatters like glass, therefore it is a game over fight for capt the second he pisses hulk off badly enough, or supes and they really unload on him that shield is going to fail eventually, it wont be easy but there is no way for him to do anything to any of those characters, he is no near strong enough to go toe to to with anything but a weak hulk, a angry hulk would shatter every bone in his body shield or no. then turn him into a gooy paste if he even tried to regenerate.
Supes maybe not so brutal but he can out speed capt without even trying not even going into the whole strength difference.
So really how much would that shield really mean in either case?
captain america is a fairly weak character period,i think it is near laughable to even try to put him on any OP list and he sure as hell cannot even hang with any of the big boys speed or power wise, he is a tactician more like batman.