Nice, looks very well made.

It does force everyone in your organization to not only use React, but also Styletron which might be a pretty large switch for some teams. Has this been a problem?

I think this could lead to limited adoption in some organizations because autonomies teams want to keep delivering with their current stack.

One idea I considered is to have an Atomic CSS library for theme stuff like whitespace, color and typography, and compose those into components for React or Svelte 3 or whatever is hot right now.

All other styling could be done with Styletron, styled components, or plain CSS, whichever suits your team.