Because it's open source, Google can't put their objectionable code directly into Android - that's what their proprietary apps and services are for, and those are where you begin to lose your freedom and control.
Also, building independent operating systems that reach as many devices as android or android based distros like LineageOS do is next to impossible because of driver issues. In fact, it's only thanks to standardization pushes by Microsoft that you can build a single ISO and run it on different IBM PC's. There is no such standardization push by Google. They are okay with each vendor forking stuff, changing source code, and then providing their own version of Android instead of requiring one google-built binary for all devices. This has detrimental effects on anyone wanting to build an alternative to android because they need to maintain a large number of kernels sometimes with millions of lines of diff to torvalds mainline. There are some meek pushes by Google and other parties to mainline more stuff to Linux and implement ARM GPU drivers in Mesa, but I doubt that we'll get a situation that's equally nice to the IBM PC situation any time soon.
PureOS is not yet ready for prime time, but it will be very interesting to see how it performs compared to AOSP when it's released. And pmOS will most likely manage to support many PureOS components on existing hardware, although obviously at some cost in reliability and privacy compared to running PureOS on Librem's supported platform.
https://itsfoss.com/open-source-alternatives-android/
By the way PureOS seems a good shot.
I just can't understand people claming to run free of Google and stay on Android !!! ;) ;) ;) ;)
Good luck with your fight againsn't the Google devil. Me ? I am staying on Apple devil device, but I just take responsibility for that choice.