Wasn't the unwieldiness of render functions the entire reason JSX was created?
Not sure of the reason, but it's a godsend comparatively. The reaction against JSX I find to be largely by people who've never actually used it.
If you keep your components small, as is best practice, whatever gut reaction one feels to it (which IMO is misplaced to begin with) is minimized, and quite readable.
ah, and the article also mentioned https://github.com/developit/htm which pretty much provides what JSX does, just in a lot less complex way (at the cost of a little run-time)