This seems like a good place to say I really enjoyed watching the video of your talk from Deconstruct Conf 2017 (https://www.deconstructconf.com/2017/kevin-lynagh-choosing-f..., referenced in your medium post) about your design process in removing CSS - gave me some nice insight into the thought that should go into the complexities you expose to users.
Definitely worth a watch for people interested in designing software for use by other people.
I should also say that I think CSS is great --- there's nothing like trying to come up with your own solution to make you appreciate the tradeoffs that other folks have made.
We had the advantage of starting from scratch in a more constrained problem space of UI layout, rather than CSS's reflowable documents + UI sometimes + 20 years of backward compatibility.
Definitely worth a watch for people interested in designing software for use by other people.