And since you won't be able to modify web pages, it will also mean the end of customization, either for looks (ie. DarkReader, Stylus), conveniance (ie. Tampermonkey) or accessibility.
My guess is that they will have people pay for a subscription to have no/fewer ads. Either they make money off ads or they make money off no ads, it's a win/win for them
I wouldn't say so, I'm not so much into buying lots of things and spending money, and I put thought behind my every purchase, but there are still quite a few purchases I've made because of ads.
I didn't regret them, but it shows that ads do work occasionally, or more often depending on the person.