Not saying Medium is perfect, but it does help standardize the display of all these random, one-off blogs.
In my opinion, the style of the blog is as important as the content because we are dealing with the self-expression of a person here. The colors and fonts were conscious decisions, and presenting the data in the most efficient and standardized form is not the first priority.
(Also calling it a "one-off" blog is kind of mean. Sure it might the first and the last time you ever read a post there, but that blog has more than one hundred posts, so it's not a "one-off" for the author.)
It's fine if you don't like it, but then say that.
Say "I didn't like the typography and colors, I prefer $style" if you really have to, but still, why?
Bright on dark, fixed width, sans serif.
Pretty much the colors and typography of programming from the first terminals, and with some interruptions, lasting into the modern day. Noting the audience, the style could be said to be fitting, especially with the current retro trends.
I agree, for a much wider (programming) audience, Medium would suit better for this blog.