I believe the value of cryptocurrency is to neuter governments' abilities to inflate or devalue currency with the push of a button, and to improve our ability to transact freely with one another.
I absolutely agree with you that money needs limitations, such as hard rules on supply increases. A money supply that is uncontrolled in such a way that you can make more or less whenever you personally feel like it regardless of the other users' intentions won't be useful for very long.
I personally think of cryptocurrency like a constitution but for money - whereas before whoever had the biggest guns could decree How It Is Now, the guns will be powerless to what is written down. In this way, it removes power of a select few to control the supply of money for their benefit.
I don't know how this ends. Is it a net negative to the human experience? Anarchy? The select few who got into bitcoin early wielding all the power now? Taxation falling to the wayside and a deterioration of quality of life? Each of these is somewhat possible, but as someone who has 2nd hand experience of what a country can do when it has free reign to issue whole new currencies and remove old ones or devalue the existing one into oblivion, I don't really care.
Let's ride this puppy and annoy some people.
EDIT: some phrasing