This seems like an issue but in all my practical experience it really isn't. TypeScript becomes JavaScript with the types removed. Then you tree-shake, minify, and whatever is executed is no where near what you actually wrote but at the same it totally is the same because that's no different than any other compilation process.

Occasionally, I have to remember that JavaScript has no types at runtime but it's surprisingly not that often.

I mean what makes it more acceptable is that you have HMR and instant preview during development. So, all the transformations and bundling aside, you do see how it runs during development.

However I have been in a few situations at work where all of a sudden we did have issues that required us to dig deeper. There were also some bundling related issues that caused problems in production deployments. At that point many co workers had no idea how to even approach it to be honest.