If you're interested, here's the overview of planned compiler work for .NET 10: https://github.com/dotnet/runtime/issues/108988

Autovectorization is usually very fragile and in areas where you care about it hand-written implementation always provides much better results that will not randomly break on minor changes to compiler version or the code, that must be carefully guarded against.

It would be still nice to have it eventually, and I was told that JIT team actively discusses this but there are just many more lower hanging fruits that will light up in disproportionately more instances of user code.

If it's any consolation, Clang/LLVM is not a silver bullet either and you will find situations where .NET's compiler output is competitive or even better: https://godbolt.org/z/3aKnePaez