Most developers are writing for developers who have approximately the same skill level and knowledge

I think you’re correct about this, but I also think that’s part of the problem.

On the one hand you can have technical tutorials for technical people, but to your point assuming the audience has the same skill level and knowledge is actually a mistake - no two people share the same same life, so while it’s reasonable to assume a certain level of knowledge, you still need to consider that there may be gaps - small gaps but gaps all the same and that it’s worth being explicit about things to avoid ambiguity. A common pitfall I see in a lot of tutorials or guides is not being explicit about file paths (“just add this to the config folder” - which folder? Where?), or not correctly steering the user towards the relevant documentation about configuration values while still expecting them to insert some config file specific to their system, stuff like that.

The other end of the spectrum - the beginner, to your point might not be the target audience but a lot of people don’t realise that those folks exist. The absolute classic example I see of this is Linux for the Everyman - Lemmy is very big on promoting Linux and moving folks away from Windows/MacOS but there’s a bit of a disconnect because a lot of tutorials exist that base level of knowledge that a complete beginner doesn’t have. So they’re both not the target audience but expected to learn that stuff - and of course it doesn’t work and they stick to what they do know.

All this is to say, writing tutorials is a skill in itself and part of that skill is knowing who your target audience really is and knowing where your knowledge is his experience from working at something for so long or a basic level of understanding you expect a user to have.