I used to agree, but I'm not sure I do anymore.
Yes, social media gives anyone a microphone; non-experts can speak on advanced topics with zero knowledge. But Gell-Mann Amnesia predates social media. The "reputable sources" of yesteryear were anything but.
Experts ignored the media and got their info from other experts. That hasn't changed. The masses were clueless or wrong about most things, that hasn't changed. People were gullible and believed anything they read, that hasn't changed.
To me, the real negative change from the Information Era isn't a decline in knowledge, it's the shift towards centralized socialization online.
People were robbed of their ability to form independent social groups and subcultures, or to differ significantly from the mainstream. There will never be anything like the hippies, punks, or emos ever again. Music used to be the major "gateway" towards political and social countercultures. Now? Music is ultra-commercialized. Online movements are much more easily molded by commercial interests and TPTB. "Counterculture political views" get promoted on Fortune 500 brands' Twitter accounts. Remember the BLM protests in 2020? Police killings increase slightly in 2021 compared to 2020, and are on track to remain stable this year; about the only lasting "legacy" of those protests was that a few grifters bought multi-million dollar houses with donation money. There is no counterculture that doesn't get coopted.
Counterintuitively, something else reinforces the status quo: social media algorithms' bias towards empty controversy. Could Gandhi's peace message succeed today? Martin Luther King? Would they even be audible?
Project yourself 10-20 years into the future, with ubiquitous availability of GPT-3-style AI; will any of what you read online even be from real people? The "open web" movement is missing the wider problem. All the effects I describe are fundamental and unavoidable consequences of the web connecting the world together; regardless of whether it's "open", or kept in corporate walled gardens.
Centralization leads to winner-take-all effects. When every road leads to Rome, it marginally increases prosperity in the periphery, while it overwhelmingly drives traffic and economic activity away from the periphery, towards Rome.[0] The same happens when you "connect all humans" together. Remember the story from a few days ago, about 90%+ of online content being created by 1-2% of people? Any counterculture needs to be insulated from mainstream influences in order to truly thrive; but social media dynamics (karma, "viralness") inherently directs content towards the lowest common denominator, i.e. the status quo. The web itself, for all the good it does, is the problem. What's the solution? Don't know.
[0]: https://twitter.com/nntaleb/status/1184807240198426625 (for a screenshot of the quoted tweet: https://twitter.com/AidanHeronUK/status/1184856198648139777)