And yet, humans currently have the edge in Brood War. Humans are probably doomed once StarCraft AIs get AlphaGo-level decision-making, but flawless micro—even on top of flawless* macro—won't help you if you only have zealots when your opponent does a muta switch. (Zealots can only attack ground and mutalisks fly, so zealots can't attack mutalisks; mutalisks are also faster than zealots.)

*By flawless, I mean macro doesn't falter because of micro elsewhere; often, even at the highest levels, players won't build new units because they're too busy controlling a big engagement or heavily multitasking (dropping at one point, defending a poke elsewhere, etc). If you look at it broadly, making the correct units is part of macro, but that's not what I'm talking about when I say flawless macro.