There is, of course, the Paul Krugman quote from 1998 that by 2005 the Internet would be no more important than a fax machine. [1]
Here's Wired in 2007 saying, in reference to Facebook, "no company in its right mind would give it a $15 billion valuation". [2]
I remember, being at Google in ~2011, we used to laugh at the Wall Street analysts because they would focus on CPC numbers to forecast a valuation, which is important only if the number of clicks is remaining constant. We knew, of course that total Internet usage was still growing quite rapidly and that queries had increased by roughly 4x over the 2009-2013 timeframe.
And a lot of people will say "If you're so smart, why aren't you rich?", and I'll point out that many people who assumed the Internet had lots of room to grow in 2005-2007 did end up very rich. Google stock has increased roughly 20x since 2007 (and 40x from its 2009 lows). Meta is now worth $1.6T, a 100x increase over the $15B valuation that everyone thought was insane in 2007. Amazon is also up about 100x. It would not be possible to take the other side of the trade and make these kind of profits if the majority of people did not think the Internet was largely over.
[1] https://www.snopes.com/fact-check/paul-krugman-internets-eff...