I run all of my browsers (including mobile) with all 3rd party scripts blocked by default. Most sites that you care to casually consume will work without issue. Anything that uses a payment provider or google to login needs 2 greylist rules (which are mind-numbingly simple to click on once).

I can set it up for people that don't understand what they are doing (and I have) and they will not notice anything in almost every case.

As such, I conclude that this generalisation is grossly overstated and you probably haven't tried it to see if what you are saying is correct.