I recently started working on a project that added TS after the project was very mature. The biggest problem is the project was never intended to have types so they feel very shoehorned in and, imo, cause far more problems than they are solving. I think in this specific case the project simply should not have been updated with types.

I have worked with JS a lot and have only used TS in this one instance. I would be interested in working on a project that included TS from the beginning to see a better representation of TS.

Also, fwiw, we have solved many of the same problems with linting and automated tests. But this requires education and maintenance; it would be interesting to compare this effort with a TS project.