The problem with AVX isn’t that compilers find it difficult to emit enough of them or that people don’t often work on problems that are easily transformed to simd at all.

It’s enough if a small number of libraries use these instructions, and a lot larger number of programs can benefit.

The problem with AVX-512 in my opinion is the sparse hardware support, power/thermal problems and noisy neighbor phenomenon.

To be useful simd instructions need to be widely available and not have adverse power effects such as making other programs go much slower.