I just hate that 90% of the stuff that's announced for the next major Android version is either part of Google Play Services (proprietary) or not part of the AOSP. Android is becoming less open source by the day. I would even argue that a pure AOSP phone isn't usable nowadays.
I agree, but that doesn't explain why Google is actively removing components from the AOSP, such as the Dialer and Message applications. Fast Pair support was also recently removed.
The answer is because they only made Android open in the first place to differenciate themselves because they couldn't compete on hardware.
Now that they can, they are slowly but surely locking everyone else out to ensure their product is superior. The agreements OEMs have to agree to for Google Play are wildly anti-competitive, in my view.
Saying that no one was using the Dialer and Message applications is a straight-up lie. What else do you think are de-google ROMs using? GrapheneOS, for example, is still using it.