This is true for iOS as well as every other widely used computing platform. Android is better; unlike iOS you can build AOSP yourself without the Google proprietary parts, and unlike iPhones, Pixel phones have unlockable bootloaders so you can install your own OS builds.

Even most PCs running Linux have plenty of nonfree binaries in various firmwares and common peripheral drivers. I support efforts to make devices with fully open firmware on which you could run Android's AOSP or other open source operating systems.