Interesting view, and also true. I’m assuming you are talking about Angular and not AngularJS.
You can, of course, write ES6+ in TS since it all boils down to ES5. And also use it with other frameworks because it is simply a transpiler. However, there is a misconception that most developers believe (1) statically typed means fewer typos, (2) it’s just ES with typos and (3) it provides reliable code, and to some extent it’s true. However, learning TS is not that straightforward, you have to know about interfaces, generics, namespaces, advanced types and so forth.
This may also be a challenge for enterprises trying to figure out what architecture (code structure) to follow, and mixing between static and dynamic may not look pretty…
In short, developers must align to a certain code style for better understanding and efficiency.
Last but not least, the beauty of the web is that you have the ability to choose whatever you want, but it’s also important to be be aware of the consequences that may influence the work flow.