I don't know if a reduced instruction set can "take inspiration" from a big one, it just becomes a non reduced one. Also these examples don't feel right for me

I don't know if a reduced instruction set can "take inspiration" from a big one, it just becomes a non reduced one. Also these examples don't feel right for me: x64 has the same number of registers as CISCs traditionally did (eg m68k, z/architecture, vax). 32-bit x86 was just an exceptionally register-starved CISC. And SIMD postdates RISC vs CISC divide for a long time, both schools of architecture got SIMD around the same time. But the divide has become less relevant because originally instruction set affected chip area a lot, and there were big gains to be had by the quantitative approach of benchmarking compiled apps with different proposed instruction sets and seeing what runs fastest when transistors are spent on hot instructions vs execution engine resources. Nowadays we have more transistors than we know what to do with, and just put in lots of cores that end up sitting idle because of diminishing returns trying to speed up cores with more transistors.