That sounds like regular old cryptography, which I don't think anyone would argue isn't important. It's a very different discussion than "crypto" a.k.a cryptocurrencies.
Author is making an argument against any blockchain or distributed ledger. To quote from article. "Any application that could be done on a blockchain could be better done on a centralized database. Except crime."
I'd like to see people look past the noise of cryptocurrencies to see how important digital trust and new applications of cryptography will be as we try to scale the ability of humans to work together effectively at scale.
So, can you name one single successful application of blockchain in the real world? Apart from crime.
I believe this is exactly the point of the author - there's lots of handwavy bubblebabble about this technology, but we're now well into the second decade of blockchain/distributed ledgers, and yet to see one single non-criminal real world application.
From just before the dot-com bubble burst to when it had fully deflated, the tech stocks had lost some $5T of stock market valuation - in 2002 dollars. So no, it's completely feasible that there is $2.6T of hot air speculative investment in cryptos. In fact, considering how divorced from practical and technical reality all of the proposed crypto schemes so far have been, that sounds like a low estimate.
There is some value in providing shadow banking to the global criminal underworld, but I don't think it will be the next technological revolution.
I'd like to see people look past the noise of cryptocurrencies to see how important digital trust and new applications of cryptography will be as we try to scale the ability of humans to work together effectively at scale.