> In Lisps, the uniformity makes it harder to quickly distinguish "behaviour" from "data", which is kind of the point, but comes with a trade-off in readability.

Maybe in theory, but in practice it's easy to tell because in the case of hiccup, the data is data (as vectors) and behavior is behavior (as function calls), those have different syntax in Clojure.

Lisps are excellent at manipulating trees, which is exactly what HTML and the DOM is.