Unclear. They don't give their reasoning beyond "complicated = bad", and very specifically leave it up to the imagination of the reader.

While they make some interesting points with regards to overcomplication and scope creep, there are also good reasons why we're still not using programs like ed as text editors, such as it being arcane and unintuitive.

vi will at least helpfully point out :exit is not an editor command. Instead, ed will not-so-helpfully point out ?.