Again, I don't see how you're strongly distinguishing failure from extreme volatility? What makes an investment vehicle successful?

And perhaps, more do the point -- why is BTC maintaining a pretty high price?

Your point on liquidity only stands if you presume what I think a lot of people incorrectly presume: which is, crypto as an alternative to day-to-day currency (edit: or perhaps other generally designed-to-be-liquid thing). Which, I agree with most, it will almost certainly NEVER be.

But that doesn't exclude the possibility of crypto as long-term investment/hedge against inflation.

I wouldn't necessarily argue that "crypto in the future will definitely be a big and useful thing," but I think it's wildly premature to call it dead.