You jest, but having worked in the ad tech industry, I can say this is actually a completely viable means of tracking people. This is why you don't load uBlock Origin into your Tor Browser or use a custom User-Agent string while using your VPN. Everything you do that is different than what everyone else does (i.e. the default) is a means of identifying you. And if I could do it at that startup, certainly Google can do it in a million more ways a million times more accurately.
If the bin is big enough or merges with other bins, it becomes the new norm.
Tor Browser has a strong "disable JavaScript" option that is relatively popular; the remaining vector is then tracking images and the rule would be to check for Tor exit node that hasn't downloaded the image cookie.
Even with JS on TB tries to reduce impact of such history based attacks.
Changing your user agent is also probably a bad idea. There are other ways to detect browser, so you're pretty unique of you're using Firefox on MacOS with a Chrome for Windows user agent.
