> If you wanted to actually solve theming, what you should work for is not a constrained helper function like light-dark(), but instead a shared token schema. Today nearly every company has their own token schema and different ways of naming things in the semantic token layer. If we had a shard language here, not only would it be trivial to add light/dark theming (just redefine a few variables that are already provided for you), code could be shared between sites and inherit the theming/branding.

Isn't that the idea behind https://open-props.style/ (and https://theme-ui.com/ in JS land)?

I think it's a great idea, but hampered by the lack of adoption incentives for the very people that need to adopt it for it to become successful (design system/component library authors). It introduces constraints, but the promised interoperability is not really beneficial to the people who need to work within those constraints.