Yes, these applications do exist. The speedups mainly come from the more flexible instruction set that AVX-512 provides (so in many cases you can replace severa

Yes, these applications do exist. The speedups mainly come from the more flexible instruction set that AVX-512 provides (so in many cases you can replace several instructions with just one), plus the increased register set (32 architectural SIMD registers versus 16 on previous generations). If your algorithm isn't sensitive to either one of these, then yes, the speedups are often smaller, particularly if the limiting factor in performance is memory bandwidth and/or latency (AVX-512 doesn't help at all there), or if the speedups aren't enough to overcome clock throttling (which IMO is a bit overblown; most people cite the Cloudflare blog article from a few years ago that complained about throttling on Xeon Silver processors, but throttling is much less of an issue on higher-TDP Gold/Platinum CPUs). However, I have seen specific applications that are >100% faster with AVX-512.