For skeptics like this, I've had success bringing up the history of paper money and point out how it took ~250yrs for the idea that money was the medium of exchange to take over (1705 with John Law to Nixon taking the US off the gold standard). Initially, paper money wasn't seen as "real" and we didn't even have an idea of what a reserve requirement was let alone how FDIC-like insurance would be REALLY useful for stability. I'm skeptical myself of if cryptocurrencies are really the "next version" of what is money, but a proper historical context lends credibility to taking them seriously.

Paper money initially was -- like cryptocurrencies are today -- inefficient, had interop problems and highly volatile. The main difference is the rate of experimentation/iteration today is so much faster and we have a complex understanding of economics already which we can use as a guide. Also, back then some of the experimentation was being run at national economy scales. Cryptocurrencies are great in that we can experiment with the idea without reaching/requiring a potentially economy-collapsing scale during the early iterations.

I doubt I'll live to see the if they turn out to be the "next version" vs an interesting experiment -- I can't imagine a wholly new definition of what is money taking root in under 2 generation.