There are lots of cultural opposition movements online, like against work exploitation, consummerism, car culture, surveillance, intellectual property, etc. I can find communities on lemmy for all those topics. But regarding a more general opposition to advertisements and marketing, other than the occasional person telling others to use adblockers online (what about ads in every day life?), I fail to see organized attempts to challenge advertisements. There is a lot that can be scrutinized. Ethical concerns such as manipulation, lack of consent and just the simple fact your attention is for sale. The effects range from damage to environment, to our mental health, to harming industries themselves, lowering product quality and maintaining monopolies.