In no way do they “shamelessly promote” proprietary software. Assuming you mean the sandboxed play services, their neutured, have no priveilged access and youre 100% in control of what they can and cant do.
I’d take that above some band-aid workaround like microG, which does need priveilged access, and fails to do what the actual play services do.
There is no way to know what it really is doing and you can’t make changes to it or even see what it is doing.
So what youre saying is that you personally audit the entire code, including when updates happen, and then “make changes” when you see fit? If so, Congrats. Youre the 1%. Most dont code, can’t read it, and sure as shit dont have the ability to change anything, that’s simply a talking point for the blind trust of FOSS apps. Context (and reality) matter.