I think it's a pretty valid consern since Bitcoin still have a fair bit of catching up with traditional fiat currencies in term of adoption, and it already consumes the energy of a small country. Now picture what that would mean if everyone was using the network for every transaction. Again I'm far from an expert but to my ears that's a pretty big challenge.

From what I've understood about Polkadot it's quite far from a fiat as it's also a decentralized ledger, so why would that be so bad in comparison to Bitcoin?

*also you sound a bit angry, did I offend you?