The jankiness of JS combined with the correctness of TS really is a powerful combo. Especially stuff like string keys and const arrays as enums make safe and readable code without a lot ceremony.
The big problem is the gap between TS and JS. User defined typeguards are a usable work around but it would be nice to be able to use a native isMyType function.
Also would be nice to have constraints natively in types. Like string lengths or max ints.