That's not really the same thing, the parent says that all cryptocurrencies are 90% greed, not that 90% of cryptocurrencies are only about greed. If it turns out that even 10% of cryptocurrencies are actually not crap it will be huge news. I'm not holding my breath.
Yes... in sci-fi (and other arts and media and consumer goods) you can mostly recognize the crap when you see it and avoid it without doing a lot more than ignoring it. That's why the 90% crap doesn't matter.
With bitcoin though -- and other crytocurrencies and blockchain products generally -- you can't ignore that almost everyone around you is trying their best to get your money.
With sci-fi you can separate the good from the bad without too much trouble. Not so with blockchains.
