Hey, all you folks ought to get together and publish a guide to writing good FOSS documentation,

No. ReadMe files should be concise, explicit, and text only. UI/UX screenshots can be part of the repo, wiki, or associated website but they shouldn't be in the ReadMe.

If you don't understand the software you're installing from some rando stranger's git repo then you shouldn't install it. Period. Take the opportunity to learn more or use another tool.

Git repos are not app stores. The devs don't owe you anything.

The vast majority of software in publicly accessible git repos are personal projects, hobbies, and one-off experiments.

Your relationship with the software and the devs that create and maintain it is your responsibility. Try talking to the devs, ask them questions, attempt to understand why they constructed their project in whatever specific way they have. You might make some new friends, or learn something really interesting. And if you encounter rudeness, hostility, or incompetence you're free to move on, such is the nature of our ever-evolving open-source community.

We bring a lot of preconceived notions into the open-source / foss / software development space as we embark on our own journey of personal development. I try to always remember it's the journey of discovery and the relationships we curate along the way that is the real prize.