That's a good personal workaround, but it's not a solution to a problem - much like moving to a different city doesn't solve the problem of the manufacturing plant poisoning the water supply of the city you live in.
Adtech industry needs to be torched. GDPR was a step in the right direction, but unfortunately isn't nearly enough (I'd start with more aggressive enforcement of it, though). Something to pressure your politicians for.
I wonder if the usage of any data by advertisers was the hardest regulated, could you stifle demand for certain types of data sources. If you need to show a verifiable paper trail that leads back to a trusted acceptance from the individual user, then it would hopefully make advertisers think twice about their data sources as many technologies out there now rely on user fingerprinting to skirt privacy regulations, and could never provide proof of consent for collecting their data.
What about all the people around the world who can't afford to pay for the services that adtech currently pays for for them? Why do you feel you can make the decision to get rid of adtech on their behalf?
I'm not making the decision for anyone - I'm not the Supreme Commander of the Solar System (yet). I am merely advocating for destruction of adtech, as much as I can.
As for people using services subsidized by adtech - there's no rule of the universe that says you can either pay everything in cash, or have it free with ads. Those are only two particular business models out of space of many. Getting rid of adtech will only make ad-powered service providers switch to the next best model, hopefully a more ethical one.
The question you're posing is equivalent to "what about all the people who couldn't afford X if providing X wouldn't involve toxic chemicals poisoning their water supply?". Societies around the world consider many business models unacceptable; I'm only pleading that advertising as practiced be added to the list of such unacceptable business models.
Adtech industry needs to be torched. GDPR was a step in the right direction, but unfortunately isn't nearly enough (I'd start with more aggressive enforcement of it, though). Something to pressure your politicians for.