Not at all, RISC-V doesn't need extremely clever compilers, and instead it's designed to maximize what the microarchitectures (hardware implementations) can do, and reduce unnecessary overhead.

My reply was mostly aimed at the idea that you can move the complexity from hardware into compilers: it might be possible, but we know how to build out-of-order CPU better than we know how to build smart compilers, so you have to invest a lot more research time, and it's generally a lower priority.

Even innovations from the past decade or two, like VSDG, haven't made their way into "industrial" compilers yet.

As for the size thing:

GCC and Clang are huge (at least when you include their entire change history, which git does), RISC-V is comparatively only a tiny part of them, you should probably look into that further before jumping to conclusions.

You don't even need a whole separate toolchain with Clang or Rust, the whole "need to build GCC yourself to cross-compile" is outdated GNU tradition, not some kind of technical necessity.