that "would" in your shift argument is already reality, that's the lightning network, which transmits bitcoin off-chain for pennies, but in a decentralized way, because it utilizes existing bitcoin balances on lightning nodes for it. There is still no bank, BUT there is a more centralized "arbiter", yes. So your argument does hold about the trustlessness, though not entirely the centralization.

The one thing that's central in this debate is to understand that current currencies are built to be inflationary, which causes the need for constant economic growth. Bitcoin is not. The "bitcoin fixes it" meme is hopeful utopianism, I grant you that, but bitcoin would not carry this growth mandate in its bowels that state currencies do.