I beg you, if you are a developer of an open source app or program - add screenshots of your app to the README file. When looking for the perfect app, I had to install dozens of them just to see what the user interface looked like and whether it suits me. This will allow users to decide if the app they choose will suit them… Please, don’t think about it, just do it…
Although I understand the OP’s perspective open-source is a community effort and people should have a more proactive attitude and contribute when they feel things aren’t okay. Most open-source developers aren’t focused / don’t have time for how things look (or at least not on the beginning). If you’re a regular user and you can spend an hour taking a bunch of screenshots and improving a readme you’ll be making more for the future the project that you might think.