Economics is a unique discipline in that the technical ideas have to be explainable to regular people.  Of course, the ideas in economics are not as technical as phyiscs, but there is essentially nothing at stake in being able to explain Maxwell’s Demon to a lay person, although that is certainly a talent.

And most disciplines that must be explained to the great un-unwashed are not technical enough for that to be any challenge.

Hand-in-hand with that distinctive feature is the fact that economic ideas are about things that regular people already have opinions on (usually strong ones) [how’s that for un-dangling a preposition!] To be able to have a useful dialog with them requires that you understand their opinions and most importantly why they have them.

Because strong opinions don’t come from nowhere. There is always some logic behind them.

So to be a good economist you must be familiar with, and see the logic behind, wrong ideas. This requires you to be sufficiently dumb. Because really really smart people would never have entertained those ideas and they will find them completely foreign and not worthy of consideration alongside the correct logic.

On the other hand you do have to be sufficiently smart to know why the logic is incomplete. But that by itself is usually not so demanding.

What is demanding is to be sufficiently dumb and sufficiently smart to be able to do both, AND also to be able to explain to BOTH the regular people and the smart people the other side.

Finally, I would add that being sufficiently dumb is crucial for finding good research projects. It has to do with the elusive “non-obvious” ideas. in practice “non-obvious” means “not obvious to the regular guy.” To spot those projects you need to have a replica of the same mental infrastructure that the regular guy is equipped with.