1. You trust every ad comes from "google"
2. You think ~everyone/most have ISP-NAT (hint nearly ~no one has it and IPv6 is a thing too (hint 2. those are 38% worldwide))
But you care about uniqueness because of ad-blockers who are used by ~40% of all users, but a IP is "not" unique, nor the browser, OS, resolution and GPU and the combination of all those factors, but NONO the Adblocker is the problem.