It sounds like you're decently informed but then make obviously wrong statements like there is no use case. How can you say decentralized value transfer would not be a "reliable use case that even a minority of people get social value out of"? Decentralized value transfer is its primary use case, and solves a problem for hundreds of millions of people.

A global currency has now been established successfully (done organically too with no authority behind it), but 15 years is entirely too short of a time frame to guarantee adoption. The primary growth issue has been secure on and off ramps for local users, but that's a short term problem. Amazingly, we already see adoption in some of the poorest corners of the world before the richest. But you already know why that is: first world countries are fine paying a higher premium on every transaction because we can be more wasteful. It does offer some additional services like chargebacks, short-term debt financing, etc. Others aren't as fortunate due to local currency values, local infrastructure, etc. Also worth mentioning, sending any kind of remittance across the globe has a punishing level of fees attached as well. I don't think you are justified to say what we have right now is good enough, because across multiple dimensions it isn't for millions of people. The adoption curves for other countries demonstrates this: there is a need for something new.

Visa claims their network can handle 24k transactions a second. There are multiple crypto that can approach that throughput without much increase in waste. Lightning network's energy use doesn't scale with the volume of transactions. The security of the network and transaction volume are different dimensions on energy usage, so I think you are off on that point.

Energy waste is definitely a concern, but IMO should not be the concern for a much needed global financial network. Energy waste must come from global emission agreements and local regulation. High non-renewable energy users should be taxed more. High individual users can also be taxed more. The good thing about crypto is the tradeoff of value add vs energy used is extremely clear to everyone involved. If it doesn't make money people stop doing it, or commit a crime that can be pursued (whether or not it will be is another issue). The economics are transparent, which is extremely important.

The externalities are not worse than the alternatives, and it's fairly obvious. The alternative is no global finance network. The alternative is an unstable money supply. The alternative is continued manipulation of powerful countries to perpetuate financial repression. The continued funding of middle-men. The slow erosion of financial privacy (TBF, only 1 crypto actually improves this).

We'll find the energy savings somewhere else, such as the overwhelming wasteful industrial and transportation sectors. Crypto will continue do what makes sense economically. It will continue funding renewable energy and lift up areas with low industry potential but high renewable energy potential.

The current system loses hundreds of billions of dollars in credit card scams. But CC companies are still profitable. Wire fraud scams are up to $3.5 billion per year. Crypto has a better chance of fixing these through new security processes (there's room for custodial wallets) than the current system. The bank is already going to tell you to take a hike if you were scammed. If you can prove it's identity theft then you will typically be made whole, but even then it's not guaranteed without additional insurance.

Cheers