AOSP is a very small part of what actually makes Android on the eyes of consumers.
At the same time, we're getting articles talking about how Microsoft is now an "open source company" because their proprietary operating system can run Linux and some open source apps: https://arstechnica.com/gadgets/2019/05/microsoft-the-open-s...
There are so many apps that won't work on it at all since Google has been steadily replacing AOSP services like location with Google Play proprietary versions. If you go to the open version of location services, you'll see there's a huge note at the top that you should really go use Google's version: https://developer.android.com/guide/topics/location
And any app that requires that, isn't going to work on Android releases that don't have Google's blessing like Huawei.
The flip-side of your experience is that it highlights the existence of a large number of Android devices based on AOSP that don't run Google apps, particularly in the PRC. Aside from the Chinese market, you have a major company like Amazon selling millions of devices with their own AOSP fork on them. On an individual level, I can install Lineage OS on my unlocked devices and use apps from F-Droid as well as many others.
Play Services does have a significant foothold in many users' experiences, which bears discussion, but it doesn't invalidate AOSP. It is Android's open source nature that allows for forks and for apps to be shared across the Android ecosystem much more readily than programs developed for an actual proprietary operating system such as Windows.
Microsoft does license Windows to the same OEMs that are having fun with Android, which just like on Android are allowed to do a certain level of customisations.
Windows is not only what comes with a PC.
The only big difference is that AOSP costs zero dollars, euro, yen,.....