There are some functionality limited to google play services, but it really is not too much in my opinion.
Regarding 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..