The traditional banking handles thousands of transfer per seconds, and many many many more assets and assets types than bitcoin. All things that bitcoin is not able - nor designed to - handle.
It's like saying that F1 engine are consuming less gas than trucks. It's only valid if you only look at it from a very specific angle. Sure, in total trucks are consuming more than F1, but both in consumption per km and in versatility, trucks win. F1 engines are not ready - nor designed to - be a suitable replacement for trucks engines.
Bitcoin and cryptos consume order of magnitude more electricity than the traditional banking system if you put them in equal terms. It's only logical since one is supposed to work in zero-trust environments while the other doesn't.
No? A currency is a medium of exchange for goods and services.
The secondary meaning that you're attempting to allocate to "currency" is already amply described by the word "asset".
The two are not the same, and assets are not meaningfully regarded as proto-currencies in the way you suggest.
What? A painting is currency? A house is currency? No.
Paintings aren’t used as currency, they are used as assets or stores of value.
Similarly, diamonds are pretty rarely used to actually transact and are rather just asset stores. It goes cash->diamond->cash; not cash->diamond->something else.
Anything can be traded or bartered that doesn’t make it currency. Some cultures used beads and shells and stuff but don’t any more. That doesn’t make beads currency.
It's an investment. Detractors cite electricity usage, but overall it uses much less electricity than the traditional banking system. Also, the value of the second type of currency is only the value that people believe it has in their transactions, which is no different than the US Dollar. Since we went off the gold standard, the US dollar only has the value we believe it has. Part of that belief is that the US Dollar is rightly a bit more stable because it is artificially manipulated by the FED to control inflation.