The mistake most devs make when trying to document their project is that they only make one (maybe two) types of documentation based on a readme template and/or what their mental model of a newcomer needs.

Devs need to be actively taught that:

1. Good documentation isn't one thing, it's four. To have good documentation, you need all four distinct types of documentation.
2. What the four types of documentation are (this is discussed in the link)

If you don't have all four types of documentation, you have bad documentation.