I still don't see how you get to a cryptocurrency that's broadly useful as a currency without enough price stability for it to be a unit of account in some sense. Tesla may have accepted BTC for payment, and it might do so again, but is it really going to commit to pricing its next model at (say) 1 BTC and just let the dollar-denominated price swing wildly? Probably not - its competitors price in dollars, so if BTC goes up it would become less attractive, and its suppliers price in dollars and other fiat currencies, so if BTC goes down its marginal revenue could fall below its marginal cost.

On top of that, BTC-denominated debt is potentially toxic for the holder. Imagine if you bought a house for, say, 1000 BTC in 2016 and your mortgage was denominated in BTC. Gradual devaluation of debt is one reason that central bank inflation targets in developed countries tend to be small positive numbers. Monetary policy is hard, and despite (totally valid) criticisms of central banks' monetary policy decisions in recent years, I'm still skeptical that anyone can do it purely algorithmically and have better results than the Fed.

I still think Libra was the only token (besides explicitly fiat-denominated stablecoins) I've seen that had a real shot at being broadly used as a currency, though I'm glad that FB won't be the ones to "own" a global currency. The "problem" is that any token that's stable enough to use as a currency is inherently too stable to have potential for large speculative gains (except if you lever it to the hilt as FX traders do today) - and IMO demand in the crypto space is still predominantly driven by speculative potential.