Bitcoin critics say that the cryptocurrency should never be regarded as a means of exchange because its mostly used for speculation.
I think that's kind of a strawman, speculation itself is not the problem, the fact that Bitcoin is volatile is the problem. And it's not even because people speculate too much, it's just because Bitcoin's future is still uncertain and people are betting on all sorts of outcomes. I'm sure time will fix it all, eventually Bitcoin will become a "boring" asset and speculators will move on to other things.