To understand Bitcoin you need to forget the technology and first understand the problem. You need to understand what caused the 2008 financial crisis and how it resulted in us collectively funnelling more value into the hands of useless bankers. You need to understand that there are people who are literally spending their days playing games with each other, trading bits of paper and making silly deals and bets. If you don't understand the word "literally" or don't believe it, read more, study harder. If you don't understand a zero sum game or how this nonsense fucks up the lives of regular people, read more.

Read The Big Short by Michael Lewis. You could even start with the film by Adam McKay who also gets it. Then read Other People's Money by John Kay.

Only once you understand the problem can you begin to understand why a trustless digital cash would be good for us. Bitcoin is simply the first viable solution to the problem. If you can come up with a better one you'll change the world.

OK, suppose the whole world used a trustless digital cash. Now you cannot do monetary policy. Now booms are booms and busts are busts and we are back to the early 1900s. Great.

Actually what would likely happen is that people would be incentivized to opt-in a digital currency with a monetary policy knob, and this would again become the de facto currency that everyone uses.

The problem with 2008 was corruption not monetary policy.