Money for advertising is already a super sized network effect, making it difficult to challenge incumbents unless you're already rich,

Look, it's a radical idea and on its face, all at once, is impractical at the moment. So I suggest rather than pointing out the myriad of holes like shooting fish in a barrel, you give it the benefit of the doubt and roll around the ways it could work in your head. And what your online/offline experience would be if it were even 10% effective.

It already is that effective in a lot of the world with stricter advertising laws, and as a Canadian I do find the levels of advertising in the us landscape to be jarring. So there are examples