The blanket proposition that cryptocurrencies in general are going to fail is very different from your proposition, that most cryptocurrencies are going to fail. Look at social media: not too long ago, everybody and their cat was attempting to create the next big social media platform, and people were warning that it was all just a fad. And they were right, but people didn't stop using social media, quite the opposite. Social media is now more used and more important than ever, it's just that everthing clustered around a few winners.
That would be my prediction for cryptos: most of them aren't special enough to be useful, a lot are just pyramids schemes where the creators premined a big chunk and hope it will be worth something once they find users, but there's certainly some that are here to stay. I don't see the original Bitcoin disappearing, Ethereum is having a bit of a rough patch right now but has the potential to become a proper computing platform and I think privacy features like those Monero is offering are always going to be in demand. But we shall see.
That would be my prediction for cryptos: most of them aren't special enough to be useful, a lot are just pyramids schemes where the creators premined a big chunk and hope it will be worth something once they find users, but there's certainly some that are here to stay. I don't see the original Bitcoin disappearing, Ethereum is having a bit of a rough patch right now but has the potential to become a proper computing platform and I think privacy features like those Monero is offering are always going to be in demand. But we shall see.