>but comes at the great cost that people who aren't already in the game won't be able to acquire Ether without basically paying cash for it. That's a weird dependence on fiat currencies for a 'decentralized ledger'. (And yeah, there might be other means, but none of them are really practical for the average person.)

There's no inherent weird dependency on cash, there's only a dependency on whatever currency people choose to pay each other for work, which currently happens to be cash.

If people started paying each other in Ethereum-based tokens, you could close the loop and cash would not be a dependency.