I think its more along the lines of things are prototyped without types, the proof of concept mostly works, then people realize that types are needed to reduce bugs, improve speed, and create a maintainable base as the project grows. What people should do is rewrite from scratch using the prototype as a vague guide, but instead people try to desperately fix the prototype incrementally. Its not the types that makes things slow, its the size of the codebase, and the lack of expectations on quality and performance.