Wide (especially unconditional) use of AVX-512 faces two main issues today: There's no public commitment from Intel to phase out CPUs that don't support it. And some emulation-adjacent tools (the prime example is valgrind) do not support it.

The latter could at least be solved with some community effort, although the relevant set of instructions is quite large. It's also not specific to AVX-512. Any comparable vector ISA faces the same challenge.