My criticism could mostly be summarized similarly. The scope of what a portable std::simd can do is almost exactly the scope that you would expect auto-vectorization to subsume over time. SIMD, to the extent it is covered by std::simd, is the part of SIMD that should be pretty simple to learn.

There isn’t an obvious path to elevate it above what auto-vectorization should theoretically be capable of in a portable way. This leads to a potential long-term outcome where std::simd is essentially a no-op because scalar code is automagically converted into the equivalent and it is incapable of supporting more sophisticated SIMD code.