[HappyKasper]

That’s a bit of a fallacy - you can legitimately point out the shortcomings of something without needing to name an alternative (e.g. criticizing Ponzi schemes). In this case, though, you could actually have an alternative of simply not using blockchain. The world was just fine for a long time without it.

[thriftwy]

For Ponzi scheme, alternative is banks and stock exchanges, not "nothing".

[TheCoelacanth]

For cryptocurrencies, the alternatives are the dozens of alternate ways of transferring funds.