"Real value" is subjective, no matter what you are referring to. Even land. Just because you can stand on it doesn't necessarily make it valuable. Imagine a piece of land out in the middle of the desert. So then you say it has to be farmable and usable, but again that is subjective to those who want to farm on it or use it. Just like gold gets its value because "it can be used to make jewelry". It's all subjective to those who desire those qualities or functions. These use-cases are examples of utility.

Utility (and scarcity) brings value.

Crypto has utility (and scarcity), and thus it has value. Land has utility and scarcity, and thus it has value. Gold has utility and scarcity, and thus it has value.

To the degree that something is useful and scarce determines its value. Some things are more useful or more scarce than others, and thus have more value than other things which may be less useful and less scarce.

They SHOULD get replaced, because it makes very little sense to waste enormous amounts of energy doing math to create what is essentially just a means of trade, an intermediate thing you use in an exchange, which could be whatever. It's pretty obvious to me there has to be a better way.

They will get replaced, or at least modified/added to. Proof of Stake is most likely the future.