- Allow custom elements to be declared (With bizzare ideas about namespaces).
- Doesn't interoperate well with React (Poor compatibility with existing web standards) .
- Rely on JS so anything being incorrect means failure (Draconian Error Handling).
- Years in standards discussions with minimal traction (but are totally going to be a thing).
All who reject #XML tech are doomed to reinvent poor copies of it; who knew the WHATWG et al. would spend their time making #XHTML2 😂