There are some functionality limited to google play services, but it really is not too much in my opinion.
replyThe amount of open stuff that was migrated into the Play Services closed source blob over the years just keeps growing.
replyI still can't comprehend why they implemented FIDO/WebAuthn support in Play Services. Passkeys are extremely difficult to support in apps that don't depend on Play Services client libraries.
replyI'm not sure what you're referring to, but I was talking about the whole permissions system where the user is a third class citizen. Device manufacturers are second class citizens (restricted by Google via CDD/CTS) and the only true winner on that system is Google.
replyRegarding some concrete examples - Google can deeply integrate Gemini, but a competitor can't do this and users get no final say here either. Competitors are restricted by the permission system, Google is not restricted at all.
While rooting can alleviate this to some extent, Play Integrity is there to make sure the user regrets that decision to break free..