> The fact that you can't turn it off system wide shows the macOS leadership is asleep at the wheel

You totally can, at least on Apple's XDR displays.

Just go to System Settings -> Displays -> Preset and change it from "Apple XDR Display (P3-1600 nits)" (or whatever) to "Internet & Web (sRGB)". You lose the ability to change screen brightness (I assume because you're locked to reference brightness), but HDR is fully off.

That option only works with Apple's XDR enabled displays (internal and external). For non-Apple external displays with HDR10, there's a separate "High Dynamic Range" toggle in the display settings in the display. On some Intel macs, if you open Display preferences while holding down the Option key, another option appears to disable simulated HDR. I'm not sure how to disable simulated HDR on the internal display of current Macbook Airs.