People have been authoring html by hand for a long time before the specialization to Frontend dev even existed...

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.

I learned HTML 20+ years ago in high school.

I did not go to a front end high school.

Java engineers write lots of HTML in java docs:)

Most front end devs can’t get HTML right either.

You don't have to be a FE dev (which is largely a junior/mid-level position anno 2026) to write HTML.

I'm not and I've used it for years. With Markdown being a thing that has been less common, sure, but that's more of a zeitgeist thing.