[ParetoOptimal]

> Manual errors with Either can make it very hard to figure out where an error came from because they don't capture backtraces. So if you don't have a very specific error for each failure point you are left guessing and debugging.

Why wouldn't you have a very specific error for each failure point?

Funnily enough, I theoretically agree with your point but can't remember being bitten by it in practice for some reason.

Maybe you can help by giving an idea of a real world example of this?