How strange! I was about to add a comment that I would probably stick to SSE2 or something like that to be sure my code suits as large an audience as possible, including CPUs from more than 10 years ago, ARM, etc.
Case in point: I've been very disappointed lately when I wanted to try Ghostty on my laptop and the binary compiled for Debian failed to run due to an invalid instruction. I don't want to force the same experience to others.
This is sort of a category error. I don't know what ghostty is doing (or perhaps its distributor), but lots of widely used software (including my own ripgrep, but also even things like glibc) will query what the CPU supports at runtime and dispatch to the correct routine based on that. So things like, "I'm only going to stick to SSE2 for maximal compatibility" have a false assumption baked into them.