Part of the problem that Typescript can help solve is that JavaScript can be tricky with undefined, null and accidentally casting numbers and strings to each other. It's really a godsend for very large web apps that have large teams of developers with more than 0% turnover.
ReScript solves this problem with a much much simpler type system and stronger inference at the cost of forcing you to handle nulls and undefined as Options.
I get that typescript's decision was to model js's behavior exactly in the type system. But now having seen the costs of that and how much can be gained by relatively small constraints on js I think it was a mistake.
