In my mind i use the criteria:
Most saleable good(easiness of tradebility with a good)
Store of Value - (Scarcity, durability)
Medium of exchange - (Acceptability, Portability)
Unit of Account - (Divisibility, Fungibility)
Gold lacks so hard in portability and divisibility that it becomes so hard to use it as money. Now if you make jewellery out of gold it becomes even worse as money, because it looses more fungibility additionally.
That’s why im arguing that even when a good can be used as money/ something else at the same time, doing so would hurt it in the area you’re not intending to use it for. So in my mind i separate the two by use case. Jewellery isn’t money and my gold bar/coin is money, even tho they’re both gold, they suit different needs better. But people could do this however they prefer, but these core properties i mentioned above definitely matter for the use as money.
Because Gold lacks so hard for regular usage, people had to find an easier way to do trade. You can’t even easily divide gold for smaller payments for example. So they started to use Paper, that was first backed by gold. Then the paper was used solely as money itself, because there was flaws in the gold standard.(i won’t go in deeper now)
Now we’re going into next era and the paper and everything else is started to being traded digitally, but the old system doesn’t really fit into this natively. And Fiat itself is not a system that can even survive without constant intervention, more control and more extreme and more extreme inequality. It’s a weak fragile form of money, the debt based money creation makes it a worse store of value with everytime it’s used.
So now we have something like Bitcoin coming up, that is superior to gold and fiat in every property mentioned above except acceptability, but we know acceptability grows with adoption. We have additional features like censorship resistance, decentralization, transaction finality that just fit way better to money that is used digitally, that actually makes trade easier in this environment, we shouldn’t forget that this is the core function of money. Fiat makes trade harder everyday and is tanking the economy in the process.
It’s native internet money, not an afterthought that doesn’t really fit like fiat. I think that just by basic economical money principles, Bitcoin is the next logical advancement of money. It can fit all the needs you could think of, better, it doesn’t matter if it can be used for something else or not, in my opinion.
That’s why im making a clear separation between money and economic resource, a good needs to specialise in one of the two. Bitcoin could be useless at anything else and would still win the money game by a lot, and yet i never keep hearing them mentioning anything about this.
If you check these criteria out, you will also notice quickly that Bitcoin beats any altcoins by a lot in this, even tho it has less features. Fundamentals just matter more in my opinion. It defeats the altcoin narrative.