Aha. I think our actual misunderstanding was about what counts as "rapid" feedback; I had in mind a shorter timescale than you did.
Keep in mind two additional points.
First, we're talking about typically complex strategies that are designed to run for a long time. Usually they accept short-term variation, but think that they'll come out ahead after the noise diversifies away. But trading ideas usually have much faster feedback cycles. For example, if you think that at the moment some asset XYZ is trading cheap because of a temporary imbalance in supply and demand and it will revert to its normal valuation in a few hours -- you'll find out if that idea was correct in a few hours.
Second,...
Another month, another rationality quotes thread. The rules are: