Whatever the target processor is, when we need performance we recompile for that specific target. And whatever the target processor is, if you need portability

Whatever the target processor is, when we need performance we recompile for that specific target. And whatever the target processor is, if you need portability you compile only with extensions widely used. It's the exact same problem with x86 or arm. So.. yes, currently RISC-V is mostly made of isolated extensions, but the goal is clearly to create groups of extensions that will be widely supported.