If you can’t do fast prototypes with types, you need to get better at using types. It’s very fast to throw stuff together in TypeScript.
Having worked in both dynamically typed and statically typed software development shops, the statically typed programmers are considerably slower in general. Usually they only have 1/3 of the output as programmers who use dynamically typing. Statically typed programmers also tend to be much less ambitious in their projects in general.
They still think they are "fast programmers" but it's complete fiction.