Exciting times for CPU architectures this year with both the M1 and Zen 3 being highly competitive. The 2010s were a bit of a stagnation when it comes to performances, lets hope more the 2020s is more interesting.
There was no competition for Intel in the x86 market. They attempted to enter mobile which was a huge and growing market and they failed.
This stagnation may have fuelled development elsewhere (RISC-V?) and now that AMD is "back in the game" and ARM is making its way into server hardware and "desktop", there's real competition again.
But these days, not really. Peel back and peer at the CPU and they all look and work much the same. The CISC implementations typically convert to their own simplified instruction subset internally, and the RISC crowd keep adding fatter and fatter CISC-like instructions.
So its not really an x86 instruction set problem. The legacy that Intel (and, a lesser extent, AMD) seem to struggle to overhaul is in their architecture, not the instruction set itself.
This is proven by the M1 doing binary translation of x86 and still being faster than the Intel chips.
That’s the real kick in the nuts for intel isn’t it. I bet apple could have jumped last year or before and been ahead in native performance. But waiting meant they even beat intel at their own game, while massively handicapped.
Basically Intel didn’t need to innovate to make money the last decade. Now it’s come to back bite them on the ass.