Take physics for example. Sometimes physicists do make forecasts -- for example, eclipses. But those are the exception. Usually, when you make a new physics theory, you use it to predict some new phenomenon -- some kind of thing that no one has seen before, because they haven’t bothered to look. For example, quantum mechanics has gained a lot of support from predicting the strange new things like quantum tunneling or quantum teleportation.
Yes, prescription not prediction. Economics is very good at that too. There are countless examples where economists have thought a system implied a specific policy or effect decades before we could actually prove this was the case, for example Friedman with QE; about 40 years between him proposing it and someone actually doing it.
Just as a climatologist can't tell you what the weather will be on 1/1/2050 neither can an economist tell you what the economy will look like in 2050. We can however say what will optimize economic and social outcomes towards that date and suggest issues that will pose a positive or negative effect on the economy out to that range.
Other times, a theory will predict things we have seen before, but will describe them in terms of other things that we thought were totally separate, unrelated phenomena.
Neoclassical synthesis.
Unfortunately, though, this kind of success isn't very highly regarded in the economics world -- at least, not that I’ve seen.
I would certainly agree experimental doesn't get as much sexy time as it should but largely why economists don't like forecasting and placing too much emphasis on it is because the dynamical system of the economy is an unpredictable bitch, we can guide her in the right direction and bump outcomes along that path but putting too much emphasis on forecasting is dangerous because its so frequently wrong. If the meteorologist gets it wrong then you are going to get rained on without an umbrella, if we relied on forecasting then we would wreck the economy.
When economists do praise a model for its empirical success, it’s usually about how well the model fits the data on the phenomenon the model was created to describe. This, as Feynman pointed out, is a pretty low bar. If that’s the only hurdle models have to clear, you can make one new theory to describe each new phenomenon. If you have a million phenomena, you end up with a million models. The models probably contradict each other, but that doesn’t matter, since each model is only judged on how well it “explains” the thing it was created to describe. Which, at least in the macroeconomics literature, is pretty much what we see.
Physics frequently does just this too, should we dismiss physics because they can't form the GUT yet?
My guess is that it’s because economics didn’t evolve from science -- it evolved from literature. Back in the days of Adam Smith and David Ricardo, there was no such thing as economic data
Until it evolved from science, Neoclassical started because one economist decided he didn't like philosophy or ethics and so replaced them with empiricism. The sciences similarly have a foundation in mysticism, people describing the world on the basis of experience and religion until it had a foundation from which to correct itself and become empirical.
Someday, maybe macroeconomists will even be able to make forecasts!
Never will this happen ever.