The problem is that it isn't much better (if at all) in its current implementation. The current implementation allows tracking and identifying individual users

The problem is that it isn't much better (if at all) in its current implementation. The current implementation allows tracking and identifying individual users (this may be or may not be fixed by Google, it has already been reported to their Github issue tracker). Since it is entirely based on your browsing patterns you can also be tracked cross device (people's browsing patterns rarely change). For the moment 3p cookies are better, they can easily be erased, blocked or even isolated, and are restricted to a single browser.