I understood your point, I'm just rejecting it. If your measure of success is scaling and making massive amounts of money, then sure, all the successful website are boring. But there are plenty of interesting websites still out there. There are still PHPBB forums which "look like dog shit" but host vibrant communities. I'm not sure on what basis you would consider these communities to have "fizzled out".
I think it's clear by your response that you didn't get it.
> There are still PHPBB forums which "look like dog shit" but host vibrant communities
There are small communities that predate modern web/Facebook, which is irrelevant. There is also craigslist, and its shitty design is remarked upon constantly. It's frequented by the elderly so falls outside the scope of discussion.
You're married to the idea that design standards haven't changed, or that the web as a platform hasn't become much more sophisticated over the last ~decade.