The ISA is only part of the computer platform, and the x86 PC is the only platform that's significantly standardized between vendors. There were several incompatible 6502-based computers in the 1970s and likewise for the 68k in the '80s, and now ARM is in the same position. I don't know if there's any way this can change, certainly it's not in any vendor's interest to make their products easy to clone, that's the "mistake" IBM made with the PC. And ARM is doing well for themselves just licensing CPU cores and letting their customers do the rest.