Aluminum production and datacenter operations also use a shocking amount of energy. Apparently Argentina uses a lot of electricity. People complain about bitcoin specifically because they don't recognize any value and they're frustrated that other people disagree. If they were genuinely worried about environmental impact, they'd look at the externalities of electricity production & distribution in a more general way (cap & trade? carbon tax?) rather than arguing that one particularly visible use of electricity is immoral.

We get something useful from aluminium production.

Subjectively. Clearly bitcoin users get something useful or they wouldn’t use it, no?

we clearly get something useful from bitcoin

Alcoa owns 24-26% of a very large hydroelectric dam in Wenatchee Washington. It’s more profitable to sell their power shares then to run their plant, so the largest(also one of the best paying) employer in town shuttered their plant to sell power instead.

There are also economic impacts not just ecological.