Ocaml types are USED by the compiler to generate FAST code.

TS types are IGNORED by the JIT to generate SLOW code.

All the features that make Typescript more ergonomic for devs also allow it to generate slower JS code. AssemblyScript tries to be TS for WASM and it doesn't support huge swaths of TS because they output unusably slow garbage.

I also suspect that more than a few Ocaml ergonomic issues are due to nominal typing. StandardML's structural typing and inference give an experience very similar to TS, but without the major soundness issues (though it must be noted that ANY generics in JS will be slow unless the compiler is creating multiple function variants).