Self-hosted languages are said to be prone to overfit because that self-hosted implementation tends to be the only large application written in that language, s

Self-hosted languages are said to be prone to overfit because that self-hosted implementation tends to be the only large application written in that language, so they converge into a similar set of features (in particular functional ones). Not necessarily bad by its own, as many features in modern languages do come from FP, but that convergence is frequently independent from the originally stated goal and ultimately lowers a probability of success.