A currency serves two purposes – a medium of exchange and a store of value. So far crypto isn’t good for either, it’s tough to use (you first have to convert it to another currency and that’s costly) and good stores of value don’t fluctuate wildly in price.
However crypto is no longer a flash in the pan either, many very smart people are working developing businesses, tools, and use cases, and prices have dropped – and recovered – for the most popular currencies. The price of crypto doesn’t seem to behave like a classic bubble.