Is bitcoin mining a problem of wasting energy?
First of all, not all crypto needs to consume power, so I assume you are referring to bitcoin.
The “waste of energy” is the barrier to protect bitcoin with competence. This is the nature of PoW.
Moreover, in 2018, the total electricity consumed by bitcoin is the same amount as Ireland, the country. However, the total market value of bitcoin was about the same size of Ireland M1 which consumes much more resources than just electricity, In order to support a country’s M1. From this point of the view, PoW the consensus, actually is more efficient than any other form of modern social consensus.