I'm not an economist either... but the buying power of your bitcoin goes down if people demand more of it for a given product. If USD prices rise, the bitcoin price will rise too, meaning your bitcoin wealth is affected by inflation, and you're not protected from the Fed printing money.

You assume there is a correlation between USD and BTC. Another way to see this is this:

If USD prices rise, the price of BTC will also rise, as BTC is another product you can buy with your USD. Meaning your bitcoin wealth is not affected by USD inflation.

But the price of bitcoin is unrelated, it seems, to any real world thing.

Pure speculation.

You could say that about the value of any currency though

No. In a currency with a lot of transactions there are plenty of real world hooks to hang their value on.

The volatility of Bitcoin, the fact it can hardly be used, the fact that almost no merchants accept it....