Designing a new clean and better ISA is easy. With the current existing experience that could be done in weeks or a few months at most, to allow for the simulat

Designing a new clean and better ISA is easy. With the current existing experience that could be done in weeks or a few months at most, to allow for the simulation of how various variants run benchmarks, to determine the best variant. Nevertheless, designing the ISA is the only easy part. Then you have to write high-quality compilers, assemblers, linkers, debuggers and various other tools, and also good documentation for the ISA and all the tools. Developing such toolchains and convincing people to use them and educating them can take some years. Optimizing various libraries for which the performance is important for the new ISA can also take years. These things are what the incumbent ISAs like Aarch64, RISC-V or POWER provide.