Discalaimer: I used to work on the Google team that worked on anti-abuse for comments/ratings.
>> So in reality I would say it's probably possible to remove any review
No, it is possible to get something removed if it violates Googles policies that are designed to make sure reviews are on topic and legitimate.
>> The customer for Google is the business, not the user as Google is promoting GoogleAds to local businesses so they need to keep them "happy" to increase Ad spend.
Not true at all. I have personally told many clients who spent XXX million dollars with Google that reviews can not be touched if they follow Google policies. The customer is not the business, it is the users who trust these reviews. Google can do just fine without monetizing the reviews but will not survive without user trust. It will take 2 hours to become a global headline if Google did something like this. And if this was true no business would every have bad reviews.