MVPs change quickly. That is the point. What hurts velocity is silent breakage: a renamed field that only fails in production, a prop that drifted between components, an API response shape nobody documented.
TypeScript does not replace tests or design. It gives you fast feedback when the model changes—which is weekly, sometimes daily, in early products.
We still keep tooling boring: strict enough to catch real mistakes, pragmatic enough that you are not fighting generics at 2 a.m.