One of the under-appreciated superpowers of gradually typed systems like TypeScript is the ability to ignore errors in parts of the codebase I don't care about right now, and focus on exercising the runtime behavior of the code paths I'm currently working on, because I can always have a working program that can be executed (and possibly crash at runtime) regardless of what the static analysis tells me is wrong with it.
Without this, large scale changes tend to become extremely painful all-or-nothing affairs that have to be applied codebase wide at every iteration, and I only find out the change doesn't work the way I expected at runtime after I've already done all the work applying it to everything across the board, and have to repeat the whole process over and over again.