With Google making it more closed every year, I wonder if is it worth it. I don’t want to learn it to find a job or anything, it’s purely for open source development.

I’ve seen a few devs dropping FOSS apps due to Google decisions. Like the developer of a music player I used (Phocid):

According to him and I agree:

Because Google is essentially killing apps distributed outside of Google Play, I have lost interest in Android development and plan to switch to a different OS once my current five-year-old phone dies.

(https://github.com/TJYSunset/Phocid/issues/185)