So that's like saying Google, Samsung is not open source. Not Android.
AOSP (Android Open Source Project) is separate from Google's. Similar to how RHEL and other related OSs are separate from Linux. Even though Google contributes to Android and Redhat contributes to Linux.
Same with Linux. I don't know of anyone who runs Linux from Scratch. Every Linux distro adds non-open code, be it audio drivers or codecs and the like.
There is no such thing as "hardly open source". Either the source is open or it isn't, and the source of Android definitely is. I think what you mean is "community driven", which is not the same thing. But open source always enables community driven forks and derivatives, which there are plenty of for Android.