That's simply not true regarding crypto, please take a look at the Ethereum Energy Consumption Index. The question becomes whether there are similar solutions or workarounds that could be used for AI, but until one proposes itself it's fair to say we're stuck.

As for calling crypto a "pyramid scheme", it's no more of a scheme than fiat currency - your claim to that effect casts a shadow on the rest of what you're saying, which is a pity.