I'm fine with JSX being stricter. "HTML soup" is extremely hard and slow to parse, compared to JSX. The community gave up shipping strict XHTML to the browser

I'm fine with JSX being stricter. "HTML soup" is extremely hard and slow to parse, compared to JSX. The community gave up shipping strict XHTML to the browser because the breakage could happen at runtime, whereas JSX disappears (and shows errors) at build time, so you can't ship broken JSX.