You assume that economists are actually an expert on the economy. They aren't. That's the problem.
Economics only really has a good understanding of very low level effects, and even there things are very difficult to truly deal with. The law of supply and demand, for instance, is really less of a law and more of a guideline - the only way to actually determine real world behavior is experimentation, as there is no single equation you can plug things into to get a result out of. And that's something SIMPLE. Ask them how to fix the economy? They have no ability to do that because they don't actually understand the economy, nor how it works.
A great deal of economics is down to ideology rather than actual reality. There are a lot of economic models but they either only represent very narrow areas or they don't actually match up with reality. Ask ten economists what happens when you raise minimum wage and you'll get ten answers - three will agree one way, three will agree the other, and the other four will give you two answers each.
The problem is that the economy is such a hideously complex system that economists have no way to actually simulate it or experiment with it (unless you argue what is actually done is an experiment, but if it is, it is a very poorly controlled one with a ridiculous number of variables).
Indeed, if you look at reality, it is obvious that economists are NOT experts on the economy. How can you tell this? Because economists make their money by being paid to be economists.
The best economist in the world is probably Warren Buffet, because he makes his money by actually making predictions about the economy and then makes money based on how good they are (as well as how well he manages his business). But ask him about tax policy and he'll still likely not have any better answer than you can get via thought and intuition.
Empirical evidence suggests that economists are not experts on the economy.
So, one more litany, hopefully someone else finds it as useful.
It's an understatement that humility is not a common virtue in online discussions, even, or especially when it's most needed.
I'll start with my own recent example. I thought up a clear and obvious objection to one of the assertions in Eliezer's critique of the FAI effort compared with the Pascal's Wager and started writing a witty reply. ...And then I stopped. In large part because I had just gone through the same situation, but on the other side, dealing with some of the comments to my post about time-turners and General Relativity by those who know next to nothing about General Relativity. It was irritating, yet here I was, falling into the same trap. And not for the first time, far from it. The following is the resulting thought process, distilled to one paragraph.
I have not spent 10,000+ hours thinking about this topic in a professional, all-out, do-the-impossible way. I probably have not spent even one hour seriously thinking about it. I probably do not have the prerequisites required to do so. I probably don't even know what prerequisites are required to think about this topic productively. In short, there are almost guaranteed to exist unknown unknowns which are bound to trip up a novice like me. The odds that I find a clever argument contradicting someone who works on this topic for a living, just by reading one or two popular explanations of it are minuscule. So if I think up such an argument, the odds of it being both new and correct are heavily stacked against me. It is true that they are non-zero, and there are popular examples of non-experts finding flaws in an established theory where there is a consensus among the experts. Some of them might even be true stories. No, Einstein was not one of these non-experts, and even if he were, I am not Einstein.
And so on. So I came up with the following, rather unpolished mantra:
If I think up what seems like an obvious objection, I will resist assuming that I have found a Weaksauce Weakness in the experts' logic. Instead I may ask politely whether my argument is a valid one, and if not, where the flaw lies.
If you think it useful, feel free to improve the wording.