I dream of being able to author web content with just a text editor.
Because HTML started life as an SGML application/vocabulary, and with SGML having entities (and link process declarations/stylesheets) for exactly these purposes, there was no need to invent HTML ad-hoc mechanisms. SGML templating based on SGML LINK works in a push (event-driven) style, with fully type-checked and HTML-aware semantics, quite different from your typical pull style embedding of whole programming languages that spit out unescaped strings ([1]).
Of course, browsers never came around to implement even basic SGML features such as entities (except for character entity references), and by 1994 or so, JavaScript was already introduced, making any HTML evolution inessential by introducing a Turing-complete language into the mix.