First step: only target users in countries that you care about and (sadly) do not target Indonesia, India, Pakistan or anywhere in Africa as these are mostly where the fake profiles are.
My guess is that social marketing works ok for brands that have a strong competitive position AND healthy margins.
Teesprings product offering is far too broad to benefit specific targeting which really just leads to low user intent, which leads to huge acquisition costs. No one gets excited for tshirts.
Products outside of these hugely saturated markets do amazingly well if you know what you're doing.
YMMV of course but we did not find Facebook ads effective at anything but reaching click farms.