TL;DR is that AVX-512 provides >20% speedup compared to AVX2
It's a shame that intel isn't including AVX-512 on the 13th gen Raptor Lake consumer CPUs, and the newer skews of 12th gen like the KS processors have it fused off.
I agree however adoption of these instructions have been very slow. The additional real estate needed for these probably seemed less worthwhile when there is little to no consumer demand.
I wonder if we see more of an adoption now that Zen 4 is confirmed to have AVX-512 support.