Simple HTML is easy to do. If you just want a document with information and it does not need lots of branding and great aesthetics. That is what you are looking at as an alternative to Markdown.
This is shockingly true. Most newer FE devs I have encountered are mostly trained on the popular frameworks and lack understanding of the underlying fundamentals, e.g., they only know TypeScript + SCSS and some smattering of HTML but more often know whatever templating engine and MVC(ish) backend the framework uses. It’s really helpful to understand what the browser is actually doing and all the “stuff” the framework spits out on the other end.
Modern JS/TS devs probably not, but I wouldn't even call someone a "frontend dev" if you don't know HTML, kind of being a infrastructure engineer and not knowing how any OSes work.
It’s not just knowing HTML as in writing a bunch div tags and patting yourself on the back. If you aren’t able to achieve at least 80% WCAG AA compliance you can’t write HTML.
Most frontend devs have no idea what any of that means. But then it seems everyone who can write 3 lines of code professionally refers to themselves as an ”engineer”.
Yes, it's literally about being able to use HTML effectively and knowing what you are doing, then you know HTML. I'm not sure why you bring up some arbitrary accessibility guidelines, that has no bearing if someone is using HTML correctly and neither would I gatekeep the "frontend" label on some arbitrary "must pass this particular standard", never heard something so outlandish when it comes to who could call themselves frontend developer or not.