Also, if you’re building binaries for redistribution, requiring Haswell or newer is kind of an aggressive choice.

I have a box that old that can run image diffusion models (I upgraded the GPU during covid.)

My point being that compiler authors do worry about “obsolete” targets because they’re widely used for compatibility reasons.

"Haswell or newer" is a bit misleading here, because there were low-end Celerons and Pentiums shipped for years after the release of Haswell that lacked AVX2 and wouldn't be able to run software compiled for -march=haswell.