The abstractions and tech which cryptocurrency works on is fragile in most of the same ways as the layers that came before it (credit cards/banks/etc). Try to look at all this holistically. How many people and resources do we dedicate on this planet to keep track of money, economy, mine the coins, cash the checks, swipe the cards, keep the lines working? All of these abstractions make trade faster and more liquid but…
Without making a comment on the crypto/tether aspect, I just want to express that it seems to me that the "cause of keeping track of 'who owns what'", as you put it, is precisely the singular technological achievement which has enabled the "human condition" to evolve to its current state. Money is literally the decentralized, asynchronous, dynamic, and continuous computation that has evolved to process the combinator…
I liked that thought, however, I don't agree with the sentence that followed it. We can do way better than that, if we're designing the "next gen" currency, it better give us way more productivity.