As I usually say, as long as at least one more broken there exists or will be released, every other cards will end up being very balanced.
No reason to limit SR/UR from any box or structure decks.
Only ones worth limiting are free SR/UR from legendary duelist that are too easy to obtain like Amazoness swordsman and enemy controler until Konami makes those available only from boxes too.
Yeah Banlist is supposed to make the game Balanced, it was easy for them to Balance Six sam back then because they only need to ban R cards. However Dm is almost the same as six sam back then (when they go first most of the time they win) But the cant nerf DM because the card that makes that deck consistent is a main Box UR.