>Completely made up and fairly meaningless

That's the total value of bitcoin at the moment. How is that made up and meaningless?

Market cap is frequently a less-than-useful metric, but for a "currency" like Bitcoin, it means almost nothing. We have no idea, really, how much is circulating, how much is permanently lost, and there's no transaction where the market cap really plays a part.

The value of bitcoin seems to trend more and more towards being a digital wealth store over a currency. In that case BTC "market cap" is a somewhat useful indicator of how much wealth is stored. It's rough but market caps in general are, especially early stage companies.

Well, you can calculate exactly how much is circulating on the blockchain, though off chain places like exchanges and the like represent even more volume.

Curious why this statement of fact is being downvoted.

ah, you're right that is a standard measure for market capitalization

It does not have absolute meaning, but it is a good relative measure -coupled with order book depth-.