Nothing makes sense about Libra. You're shifting control of a decentralized currency to the power of technocrats. You've literally swapped one evil for another. China is trying to do it because if you control the blockchain, and build in enough bugs, you create a permanent transaction record for every single citizen who uses your stuff. In fact, by knowing the blockchain addresses of a dissident you can effectively shut off their ability to function in the economy with a button click. The problem gets worse when you realize the transaction history would be historically permanent. Imagine you like expensive whisky and a teetotaler gets into office. They instantly look up the transaction history of everyone who bought whisky and ban you from the market. How about a previous smoker? Insurance companies mine the blockchain for ex-smokers and charge them exorbitant rates, effectively cutting off there ability to receive even a simple check up. A trackable blockchain is frightening.
This makes it no better than a debit card, and some form of "crypto cash" will be necessary to circumvent this. Tumbling really doesn't solve the problem long term.
Bitcoin was more of an intellectual project than an actual solution. There will be more coins, and eventually one of them will do it right. Obviously this will take longer than average because you don't have high profile economists working on the problem (governments really, really don't like cryptocurrencies).
