What do you mean if? The internet is built on html. Markdown is a random flare up of an annoying annotation standard pushed by LLMs. No one used Markdown anywhere near at the scale of html before ChatGPT
Thats a complete reductive idea of MDs. MD was long spawn before LLMs as a need for light weight formatting and easy conversion to different formats. No one used at that scale doesnt mean the absence of the utility for it, as the primary adopters were tech community and that was a layer below the consumer market. Utility obviously stands, the question is, can HTML supersede on that utility side of it in all developer work components.