I'll ignore the unnecessary personal attack in the first half. You were the one that accused me of being too invested in bitcoin to change my mind, and I retaliated by pointing out the reverse can be equally said. I'm certainly not using it as some sales technique or reason to invest.

I can see why Satoshi Nakamoto famously said "If you don't believe me or don't get it, I don't have time to try to convince you, sorry.". This is quite tiring and we aren't getting very far very fast. Please don't turn this into another lengthy character slur and let's focus on bitcoin itself.

Yes I agree that technically the miners do vote on what bitcoin is, but they have no more power than the light-weight validation nodes. Ultimately, its the people that decide what bitcoin is, not the miners.

So onto the energy expenditure:
I completely agree that the energy expenditure is used to secure the network and the transactions within blockchain.
I also completely agree that most people would see the energy expenditure as a waste. On the face of it, it's massive amounts of energy that's just flushed down the toilet in the name of doing some maths problems, almost all of which are discarded. It's absolutely true. I get it, okay! How can it not be a waste? It only took a 2 minute conversation back in 2012 for me to write off bitcoin as a waste of energy for 8 years on this very basis!

The fact is that you have to zoom right out and see a much bigger view to understand why it's not a waste of energy and is actually the opposite. This is where the problem bitcoin is trying to solve comes in. And once you see the whole picture, it becomes clear that bitcoin has solved the problem in the most efficient way possible. In fact it's a work of art. It's beautiful.

So we've dealt with the technology side of things to the point where we have enough agreement to discuss the bigger picture.

There's a couple of maxims to lay out first:

The first maxim is that if we double the amount of currency units, each unit will gradually have half the value compared to if we hadn't.

The second is if it's possible for humans to create money without exerting work of equal value, then they will take advantage and inevitably create more and more money. This has been demonstrated throughout history and is currently repeating once again with the fiat currencies around the world. We can't trust - we have to verify.

Combining those two maxims shows us that if we give certain humans the ability to print money with less effort than the money is worth, then they are essentially incentivised to do this as much as they can get away with. They get to create and spend the money at the current value while it slowly goes down in value as the rest of the population spend it. At the extreme, where they can create the money for free (e.g. centralised digital/paper money) then they essentially have a faucet of free money, the value of which is sucked out of the money owned by the rest of the people.

Along with it's other fundamental properties (divisibility, portability, fungibility etc), the reason why gold stood the test of time as a good store-of-value was because there is no way that you can mine gold without exerting at least as much energy as the gold is worth. If the demand for gold goes up, the price rises, more gold miners are incentivised to mine and the increased supply brings down the price again. In reality this has stabilised at an average supply inflation of 1.5% - the amount of above-ground gold doubles every 50 years.

Even though this natural tying of value to mining effort has maintained the scarcity of gold for thousands of years (about as well as it can be done in the physical world), the other monetary properties of gold were not a patch on the later paper money that represented gold and so bank paper took over the role of money in society. However, in accordance with second maxim I gave, it wasn't long before bankers figured out a way to print more and more paper currency without people realising and ultimately we now have digital fiat currencies that they can "print" almost freely with no limit.

This leads to a massive wealth transfer due to the Cantillon effect, which ultimately can be seen in the currency unit leaking value right out of your hands. You can put your money in a concrete vault buried 10 miles under ground and still the bankers can steal the value out of it by simply turning on the money printer.

So in order to fix this, and obtain a better money, more like gold but with the digital qualities of fiat, standing on the shoulders of giants, Nakamoto solved the long-standing computer science problem for decentralised digital currencies - the double spend problem.

Essentially bitcoin solves the problem of a digital asset with scarcity. And history shows that the only way it can do this is to require that the creation of the units of the asset demands the same amount of work as the unit's value.
We can't simply trust humans not to create more, cheaply (or as you might put it, efficiently).
Money is energy. And it's perfectly natural to require the same amount of energy to create it. If it doesn't then the value in the existing money is essentially stolen by the people creating the money cheaply, to make up the difference. You simply can't break the laws of nature in this way. Money is energy, and you can't create energy out of thin air, you can only convert it from one form to another. I know it's not physical energy. It's a more abstract form of potential energy.

The proof of work required by bitcoin is an abstraction of work. It could equally demand proof that miners have dug a hole and then filled it in again, before being rewarded with newly minted bitcoin of equal value. It turns out that getting them to find the nonce to generate a hash within a range is a form of work impossible to fake, and is in a digital form native to the network. If we try to make the work they do useful in some other way, they can monetize it and are then essentially getting the freshly minted bitcoin for less than the net energy they exerted (their energy cost is offset by the monetized returns of their "useful" work).

Understanding and seeing money as energy (or more accurately, a container for energy) along with the then obvious constraints on creation in this way is crucial to understanding why any sound digital money requires equivalent work for its issuance, and any alternative will simply lead to a weak money that goes to zero in time. You can't break the rules of nature.

Bitcoin doesn't need to be a currency - all it needs to be is a liquid asset, with hard scarcity, accessible by anyone in the world, and it will succeed.

Success to some simply means it will go up in value enormously and make them fabulously wealthy and free. To last adopters it means they can store their wealth without it being stolen, or having to gamble it on the stock market , or buying extra housing enslaving yet another person stuck in the rental trap. To others it means that it provides an escape hatch from the enormous wealth transfer system that's central banking, ultimately shutting down the central banking scam, and fixing so many of the problems we see in the world caused by it (wars, third-world poverty, government corruption - the list gets longer the longer you look)

The fact is that first it needs to prove itself as a store of value. As it does this more and more people will store their value in it. Once it has saturated its market and the value as stabilised, it will be suitable for unit of account and certainly medium of exchange on an inter-bank, inter-nation scale. Once enough people have enough of it and once it's stable enough to be used as unit of account, only then will we need to worry about it being capable of medium of exchange to buy your coffee with. If all else fails, it will run on centralised payment rails like Paypal.

In the meantime, the current banking system/government/media machine will do everything it can to kill it, as it takes away their power. Somehow magically, it turns out that it seems there's nothing they can do to stop it. All they can do is eventually accept it and join it. But that's probably something for another day.