So, just like every app I use that doesn't put effort into making me aware of their new features (but probably worse, as it likely takes more effort to find those features).

It's humbling (and annoying) when you think of yourself as a power user of some application to find out from some semi-new user of it that there's a new feature that would have made your life much easier if you had only known it was added a year or two ago.

There's only so much time to learn about the tools you use, much less the changes in them over time. How do I find out if GNU grep has some interesting new feature in the version that ships with the next version of the distro I use? Or rsync? Or tmux/screen?

This problem definitely seems worse with smaller tools, since there's a lot of them and they are often packages together by some other party. Not every project is as large and used as much but such a large population as Firefox, which arguably does a very good job of advertising new features. But you can definitely tell it takes them a lot of time and effort to do so, and a smaller project may not find much traction if they tried the same strategy.