Bitcoin is the only really useful crypto that fundamentally has no reason to die because of basic economics. It is fundamentally the only hard currency we have ever created and that's why it is revolutionary

I find it hard to accept the statement that "[bitcoin] is fundamentally the only hard currency we have ever created". Is it saying that gold back currencies were not created by us, or that gold isn't hard enough?

Additionally, there's a good reason we moved off deflationary hard currencies and onto inflationary fiat currencies. Bitcoin acts more like a commodity than a medium of exchange. People tend to buy it, hold it, and then eventually cash out. If I am given a bunch of bitcoin, the incentive is for me not to spend it, but rather keep it close and wait for it to appreciate — what good is a currency that people don't spend?

Also I find it weird when I read that due to its mathematically proven finite supply it is basic economics that gives it value. Value in modern economics is defined as what people are willing to give up to obtain that thing. Right now, people are willing to give up a lot for bitcoin, but mainly because other people are also willing to give up a lot for bitcoin, which gives it value.

It's a remarkable piece of engineering that has enabled this (solving the double spending problem especially), but it doesn't have inherent value in and if itself. There are many finite things in the world that are not valued as highly as bitcoin is. There's a finite number of beanie babies, a finite number is cassette tapes, a finite number of blockbuster coupons...

Gold is similar — should we all agree tomorrow that gold sucks and should never be regarded as a precious metal, then it won't lose its value completely (there's only a finite amount of it, and some people will still want it, e.g. for making connectors). But its current valuation is far higher than it would be for its scarcity alone — people mainly want gold, because other people want gold.