That argument could even be somehow valid if it were only possible to demonstrate that these intangibles improve life for people, like contributing to food, housing, education or even only entertainment. They do not. We do not have to care for those who are affluent enough to burn electricity just in order to gamble. Those people have the resources to gamble in less harmful ways without raising electricity prices and polluting the air the way they do. Those people could even do something helpful and productive if they chose to. Cryptomining is wasting energy for the sake of wasting energy. You may argue we (the 99.999% who do not cryptomine) are too stupid to see the value of your imaginary intangibles but that's not true. We are the ones who want no part in a pyramid scheme, who do not want to succumb to gambling, and whose time and money are too scarce and too precious to be put on the line. Sure, all activity has its price, its waste, and sure, there are other occupations whose overall usefulness is doubtful and askew with the accompanying resource consumption. Doesn't mean you have too excuse bad behavior just because there are other guys doing no good.
Just as an aside, when you move a newspaper or a magazine from print to only existing as a web page, you certainly have 'dematerialized' it to a degree. However you still need hardware to keep and display the data and energy to move it around and light up the screens. In so far it does not stop being physical. The 'intangible' is somewhat of a red herring. Yes, it is less haptic, but it's still physics, physical all the way down. Other than that, currencies, freedom, equality, education, entertainment—we've been having intangibles all the time, at least from the dawn of human culture onward. Cryptomining does not bring anything genuinely new to the table in this respect. It's not even new in being a fraudulent, volatile scheme that betrays traits of a cult, one that benefits a few and hurts the many.