the Bible puts the Earth and humanity as the focus of creation.
Well not necessarily (because it doesn't actually say that), but certainly the Bible's focus WOULD be this planet and humanity, otherwise what meaning would it have for those who inhabit it?? the text is supposed to apply to us, not another galaxy or planet but that doesn't mean humans are the only focus in the entire universe as there could be many galaxies that have inhabitants IMO, then there are the heaven realms beyond the physical.
According to Genesis, God spent nearly all His time creating and populating the Earth.
Again how do you deduce that? No txt says that and I don't see how it follows that God is not doing other things and other things within our universe.
Billions of stars were thrown in almost as an afterthought at the end of day 4.
I'm not a Genesis literalist so there's no reason for me to assume that God had/has no process of creating the universe and I have no reason to assume that stars aren't for other planets as well. Another conclusion that doesn't really follow.
And their purpose? To provide light for the Earth.
Provide light for the earth and any other planet that needs light.....as well as seed the entire universe, again no reason to believe humans are the only ones that occupy the universe or that God is not using stars for other planets.
If that is not egocentric, I don't know what is.
The txt is referring to us because its' about us in the same way you'd want to learn about something that is relevant to your experience, that doesn't mean that the stars only purposes are JUST for earth alone, even if it were that's how God wanted it. However I don't need to make any extra assumptions when not necessary. In what way are you referring to "egocentric" anyways? because there's a difference in understanding that God did in fact create the universe for all forms of life but in no way does that equate to "without regard for the feelings or desires of others; self-centered." It's not our fault God created stars for planets, so that it would play a role in sustaining life. So who or what are you claiming is egocentric?