Does it, though? I'd actually like to see a thorough study done on this. My hypothesis is different from yours: the proliferation of "specialty sites" is a product and symptom of the walled garden phenomenon, and further serves to sequester and censor undesirable content from the wider audience.
What are you suggesting is better, though? really, that we all just publish one of 10000 articles to dev.to and hope their search and popularity algorithm puts your article in front of peoples' eyes? That everyone should upload video to a single time-ordered feed that you have to scroll through until you find something you like without algorithmic involvement? Im seriously confused, how do you do content selection or personal curation in a world without niches
I seem to recall a survey in South East Asia asking people about their internet use, and there were more Facebook users than internet users...
Ah, here: https://qz.com/333313/milliions-of-facebook-users-have-no-id...
"11% of Indonesians who said they used Facebook also said they did not use the internet."
I remember a rash of such loaded survey questions going around my country a few years ago, it looked like it was specifically designed to be answered with answers that could be used to slander my nation with "N% of these people think this" results. It's usually not disinterested parties investing the time and resources to run these survey, rather, it's usually people for whom the investment will pay off if they can get the results they want.