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, the strategies I mentioned have already passed a very high bar -- they convinced a sufficient number of people that they are good enough to commit real money to. At the research stage, figuring out if a strategy looks decent takes a few minutes-- you feed it to a trading simulator based on historical data and look at the results. The strategies in the grandparent post are the equivalent of clinical trials in pharma -- there are already a lot of people convinced they would work.