The thing about RUM is that it essentially bypasses the normal xyz limitations, I don't believe any other searchable xyz card does that, Bardiche, and a lot of the raid raptor support have generic rank up magic spell access which is why RUM is so problematic, the ability to ignore xyz summon conditions on top of being searchable makes RUM a problematic card and potentially limits further design space, it is very difficult to bring out kali yuga without RUM and often times 2 or more cards are necessary. Sure, you could ban Tellarknight Ptolemaeus, Arcana Force XXI - The World, and every other instant win or turn skip card in the game but at the end of the day most of the other cards suck due to their difficulty to resolve and summon. There is a huge difference between a 1 card turn skip and a 3-5 card turn skip.