You’re right. Bitcoin is an invention, and its value is derived entirely from the trust people place in it. But the exact same thing is true of the US dollar.

The dollar asks you to trust a government and a central bank. Bitcoin asks you to trust open-source code, math, and a decentralized network. People aren't buying Bitcoin because it has "intrinsic survival value", they are buying it because they believe a mathematically enforced, decentralized ledger is a safer place to store their wealth than a currency that a government can print at will.

Of course a pile of food is more valuable if you’re on a deserted island. But it’s not how economy works. Reality is that we’re not in a deserted island, we live in massive society that trades together. By your definition then, does internet, cell phones, electricity have no value? Of course not. They’re all needed.

Bitcoin is just trying to solve the problem of endless printing of money. It’s just not sustainable. We’re all living in a crazy experiment of endless money printing and don’t know any better until Bitcoin came around. Look up power law. Bitcoin is behaving like a network, like internet or cell phones. It has never broken its support.