I read the linked post. Cowen makes no statement that crypto is a great thing. Nor does the FTX scandal reflect on cryptocurrency, it was simply a scam. "Defi" also was not decentralized, not really finance, unconnected to cryptocurrency save that it was transacted in cryptocurrency, and also just scams ("If you don't know where the yield is coming from, you are the yield")
Bitcoin seems to still be operating fine. Useful, no sign yet that its revolutionary, no connection with FTX or the other recent blowups.
Maybe crypto is just a thing and neither great, nor terrible