Earlier quoted context omitted.
>Typescript will not help us a dime with type checking for most of devs we hire are long past the stage when typing errors are a thing for them. Who are these mythical people? Do they just magically decipher what interface an argument conforms to? What methods are accessible on a returned result from any random library they're using?
I'm not a myth. Some of us started JS programming over a decade ago, with no strong typing and IDE to hold our hand and tell us every time you make a mistake. The key is just discipline, good design patterns and a good linter. I see TypesScript as a VERY opinionated linter that affects how you think and write JS. JS is a dynamically typed language, which means you loose a lot of its power and flexability by shoe-horn…
For what it's worth, my experience with programmers who think like you is that rarely they're actually genuinely talented and right, and mostly they just spew forth bugs which often sit dormant until they rear their ugly heads years later. Most people are better off thinking about their API's before they implement them, much like one would do in a real engineering discipline. Types are often (and yes, not always) a good way to draw the effort out to the front of your process.