New theories and new software

Here's an excerpt from Dwarkesh Patel's interview with Terence Tao that's stuck with me: Often, the ultimately correct theory initially is worse in many ways. Copernicus’s theory of the planets was less accurate than Ptolemy’s theory. Geocentrism had been developed for a millennium by that point, and they had made many tweaks and increasingly complicated ad hoc fixes to make it more and more accurate. [...] When you only get part of the solution, it looks worse than a theory which is incorrect but somehow has been completed to the point where it kind of answers all the questions. I often think about this now when I'm doing migrations (which is often). The new system can be more correct and still perform worse, because the old system has more fitting (or overfitting) to the relevant tasks. Some of these legacy-system features tend to be good and noble: for example, handling observed (if unofficial) bad inputs that are hard to anticipate a priori. Some are not: for example, handling a…