> Technically html + css + user interaction can be turing complete: https://github.com/brandondong/css-turing-machine

Turing completeness is about what computations can be expressed, not what user interactions can be performed. The lambda calculus is Turing complete, but, if I whip up a lambda calculus interpreter and don't give it a print statement, then you'll never know anything about the computations it's performing.