In recent Android versions increasingly more features got moved into proprietary modules. A few years ago AOSP felt pretty much the same as proprietary Android.
Now changes in toolkits made it so that e.g. copying text from apps sometimes doesn't work. Google Android has a work around by using OCR (?) in the overview to select text. I feel like the former change is directly related to the ability of the OS to copy text anyway. This might not be a deliberate choice to limit AOSP but it shows how they design with proprietary Android in mind. Thus AOSP gets less useful as an OS as the design is not well thought out.
Now changes in toolkits made it so that e.g. copying text from apps sometimes doesn't work. Google Android has a work around by using OCR (?) in the overview to select text. I feel like the former change is directly related to the ability of the OS to copy text anyway. This might not be a deliberate choice to limit AOSP but it shows how they design with proprietary Android in mind. Thus AOSP gets less useful as an OS as the design is not well thought out.