Individually, you have a choice. But not using e.g. WhatsApp needs to be a collective decision or it won't work because everybody else is still stuck in there.
The decision to be the first,... to lead,... to tread without trepidation where others fear to go,... that's what I called growing a spine. "Won't work because everybody else is still stuck in there" is simply an expression of that fear.
Same goes for every other communication tech. Just because your endpoint is not spied upon, if every other endpoint is spied upon you gain nothing. If you don't use WhatsApp, but all your friends use WhatsApp to talk about you then you gained nothing.
If you really believe there is no such thing as collective decision-making then imho you already gave up in the fight for privacy.
But even if we boycot Google and Facebook, they are not the main problem. Their business model is the main problem. Spying on your users, training predictive models, and using those models to exploit people is simply too profitable, and therefore too attractive for any profit-seeking company to ignore.
Until we solve that problem by deciding as a society that these business models are not ok, this 1984-like world we currently live in will be our reality.