The AOSP is a huge success and phones are really only the tip of the iceberg, android runs everywhere and is basically responsible for the mainstream adoption of “smart” devices.
It’s a small OS that runs on basically anything and you can stick it on most computers regardless of how strange the hardware setup is.
Is it perfect? No, as a project android is basically maintained by Google alone and Google obviously doesn’t think it’s perfect, or fuschia wouldn’t exist.