Quote from BlueTronFTW »The problem with Twin is that you either have those other blue decks you are referring to, or twin. No cool UR Pyromancer (which top 8'ed a pro tour this year, just saying), no UW control, no grixis shadow, no jeskai flash, no UR breach, no madcap experiment shenanigans. It all becomes Twin.
Repeating this line over and over does not make it true. But other decks existed concurrently with Twin, just as they would if Twin was legal today. I've been banned fighting this line of revisionist history in the past, so I will leave it at this: Other builds would survive as long as they were strong enough do to so (or had passionate enough followings), just as they did in the past. If they do not survive, it has nothing to do with whether or not Twin is around, and everything to do with those decks just not being good enough in the current meta.