Cash or credit. Doesn't matter there's always opportunity/alternative cost. If you have a bag of resources you have to decide what to do with it, and for that usually you need to evaluate a bunch of possibilities. This is the same as ranking them by utility.

ROI is just one kind of utility function, but converting everything to said resource-equivalent works pretty well.

It's always a nasty burden to decide between hospitals and roads, but it's a neccesity also, because building just hospitals without roads doesn't help much, because ambulances can't get to them. And vice versa.

Sure, ROI in itself is a bad metric, and the problem is that developed nations are frequently get caught in an overly simplistic financial modelling situation. Because politically a more complex model is very hard to defend and the simple model gives simple answers, which are usually not optimal.

As you said, creative solutions are what's needed, but they are harder to quantify.