Some good points, but missing the most important understanding of what cryptocurrency actually is at it's core. Once you understand this, you will see that although humans are treating the technology idiotically as they do everything, fundamentally it's a basic and critical advance. And arguing against it is holding back society.

Cryptocurrency is just the best contemporary approach we have for applying computer science to money. That involves cryptography and blockchains because they are the most relevant technologies for accounting.

The typical alternative is a database from the 1970s or 80s running on something like a private mainframe, that can be modified at whim by those who control it. The biggest problem with this is that when so many have a chance to cheat, some will. But the core failing of the concept is that it's a private database with no mechanism for external (or even necessarily internal) verification. The core thing that people such as yourself will eventually learn about is that cryptography and blockchains are the best approach we have for solving these problems. It's just the basic application of computer science to accounting.

Many of these systems were built before cryptography was well known, and some run on hardware that may not even be capable of current cryptographic standards.

Fundamentally, arguing against cryptocurrency is like arguing against calculus in the 17th century.