Additionally, many of these devs are arguably masters at vanilla JavaScript. Some learned JS before modern features became available. They probably don’t need ES5 features to be productive, let alone the newer features or for that matter TypeScript.
The frustration is that they would probably benefit from using TypeScript in the long run.
I resisted learning TypeScript because it felt like coding with handcuffs on.
I was sold on it when I realized how much easier the handcuffs make it to accept code contributions. I've internalized TS enough that I still get to flow state on my own code. Whole categories of rookie mistakes no longer interrupt my blissful concentration, because they are caught by tooling before making it in to a pull request.