It's quite frightening to see how an enormous 120KLOC pull request gets merged at once with very little public discussion or coverage by the devs after just 3 months (which IMO is very little time in relation to the amount of code). There used to be extensive RFCs and series of conference talks long preceding changes this big, e.g. React Fiber.

I support wholeheartedly the move to AOT-compiled languages but it looks like paying off the cognitive debt is going to be brutal on whichever team gets to maintain it in the long run.