You're telling me right here that absolutely 'no-one' is using Ethereum? Surely you are not at all serious about what you said. There are many companies like Moneygram, Stripe, Ticketmaster, Checkout.com, etc that are using crypto currencies like Ethereum which are on greener consensus models.
Ethereum made it possible to switch from a wasteful consensus model like proof-of-work to proof-of-stake and it significantly reduced its emissions by 99.992% [0]. Even if your ludicrous claim of absolutely 'no one uses it for anything either', it is not incinerating the planet or wasting as much resources and energy unlike AI (deep learning) that is currently doing today.
After a decade of deep learning, AI has no efficient alternatives to their existing operations and brings in more resource waste and incinerates the planet. Being 'useful' is not a great excuse to justify burning the planet.
[0] https://consensys.net/blog/press-release/ethereum-blockchain...
On the another hand after years of deep learning, there is still no viable efficient methods of training, fine tuning or inference without needing more data centers as the data and the AI model scales and its hype is currently contributing to the increased wastage of water and resources all for the sake of incinerating the planet to produce broken and hallucinating black-box AI models.
Being ‘useful’ isn’t an excuse for not finding greener efficient alternatives that significantly lower emissions rather than continuing to burn the planet over the new ‘hype’.