Word of mouth. Make things that work well, people want, and stand out - and they will spread by themselves. I block 100% of advertising on all platforms I use, yet somehow never have difficulty finding things when I want to find them. And that often includes stuff from very small providers. Search + reviews, and so on are a million times more useful than advertising. And getting a hundred or so early users/testers/etc to seed those reviews/etc is trivial in modern digital times.

The world itself would almost certainly be a much better place without large scale/centralized advertising. I think the argument about it providing product discovery for hidden gems is nonsense. In reality it's mostly just crap, artificial demand creation, and behemoths trying to maintain brand image.