I what way shape or form can settling money over several days be better than instant transfers with direct auth?

You can do that too! It's just that you can also use checks. I don't see the problem, instant money transfers are ubiquitous and were easy for me even as a visitor in the US. The fact that bank transferts take longer doesn't really matter day to day, they just don't use them for that

Just to be clear, I live in Australia and we also have 3 day cheque clearing but the banks and government are closing out on cheque processes and almost everything now is payid which is instant settlement. From what little I read it's more reliable than venmo.