Aren't you conflating the technical side of it with the economic one?

A bubble doesn't necessarily mean that the the underlying tech/innovation isn't useful. It's a financial and economic phenomenon that is pretty well understood and researched:

- During the hype cycle, investors tend to overestimate the short to mid term effects and underestimate the long term effects.

- It's near impossible to pick the winners in advance, and research has shown that investors underestimate how many losers there will be.

- The financial system/market works very well when there are localized issues with debt. Those get seemingly automatically detected and repaired. But broad increases in credit not so much. Those spread into the whole system in non-obvious and complex ways and destabilize the whole system, which can lead to very large corrections.

etc.