Here is my attempt: blockchain is a 'good enough' way to bootload a platform for making permissionless dollar-denominated payments. You could technically achieve the same functionality, with better performance, off an interoperable open standards database and communication protocol. But everyone from global south governments, to the CFTC/SEC, to Mastercard would be after you before liability could be effectively distributed. With the design they're going for, you can vaguely gesture to the stablecoin issuers, node operators and on/off ramp operators that will be there on day 1 as legally separate parties each carrying part of the liability.

I will end with this thought: If we can get to a new local equilibrium where global transaction costs are 10x lower and >30% of global GDP can get paid faster / with better price signals / etc., shouldn't we try even if the tech is non-optimal?

At the end of the day, you are supplanting a monopoly with another and distracting from the main purpose of cryptocurrency which is to eliminate the monopoly role altogether.