Neither Apple iOS or Android were "build from nothing in 2-3 years".
iOS is based on OS-X, which is based on NeXT, which is based on BSD (~40 years of work)
Android is based on Linux (so ~20 years of work)
My point is that they went from zero apps and zero users to lots in 2-3 years. IMO the argument that Windows backwards compatibility is the only way to get the long tail of tens of thousands of apps has been refuted.
Apple and Android have shown that you can build a mainstream platform ecosystem from nothing in 2-3 years, so who needs Windows compatibility?