I like Gemtext. It's a nice way of writing, free from the distractions of Tag Soup or Markdown. It lets me focus more on content rather than presentation. (although lipu alasa has support for a couple extensions I've used a total of two times, I'm thinking about trimming them out)
Another thing I like about Gemtext is it has just enough formatting to be more accessible than plain text. A screen reader, for instance, could recognize a link or preformatted block in Gemtext and offer to open or skip over them. Plain text doesn't have that semantic information. A screen reader would assume it's all plain, regular text and might try to read links and code blocks as sentences.
Gemtext also doesn't have stylesheets or client-side scripting that can be abused to make horribly inaccessible or content-free documents. Some Gemini clients even offer customisable colors and fonts that the documents cannot override.