> I've always been under the impression that if you make something truly useful or interesting, it will spread through word of mouth naturally and quickly.

useful or interesting stuff has zero chances in the marketplace even if you spend millions on marketing. you can put in on github for free maybe.

it is idiotic (facebook, tiktop, instagram, cat videos, etc) or harmful stuff (all the evil companies) that make the big money.

Time and time again I'm surprised how many different types of cat toys are being advertised on Instagram/Twitter by cat video meme pages. Must be a pretty big market.