Of course, it won't be private.
It will be what an advertising company thinks is best for you.
That must,fundamentally, be a conflict of interest.
But I imagine the bigger problem is that it won't be open-ended.
It will be a handful of top-down features designed by PMs to be generally useful.
Google always has the tension between hyper-bespoke features that are actually useful to people… or features that are broad but not deep.
Another way is to grow the features bottom up, where the situated actions of savvy users accumulates value that can then help other people, too.
Fractically vertical use cases.