By analogy, would complaining about any organization ridiculously more powerful than you (e.g. a government) without having a complete alternative ready to go also be "childish"?

Solutions from F-Droid? There are none. Like they said, it's an unremovable system service.

Because as designed they have to live under whatever google puts into Android because they have inordinate control over the whole ecosystem? I'm not sure why or how you would possibly describe that as "childish".