Precisely why I think "Metro" is the worst of the three, and Material Design is the best, because at least it allows for some hierarchy in design.

I've always thought Metro was terrible, but others seemed to love it for its seizure-inducing animated colors splattered over the whole screen.

Apple's design is bad mainly because it's inconsistent and amateurishly done in its mission to be "flat like the cool kids". Metro is bad on purpose.