Imho Typescript has so many advantages that NOT using TS doesn’t make sense to me. After all, TS is a superset of ES6, so you can just write ES6 all you want.
When you’re ready, you can introduce types etc.
The reason that Angular2 is easier with TS is that it supports annotations (which, by coincidence, is an ES7 standard).
It doesn’t seem like you’ve been playing with NG2 much — I find it simpler than React, and MUCH more liberating in sense to what I can do and how I can structure my application.
I am 80% through implementing a relatively large project using Angular2, and I simply love it more than I’ve loved anything before (development wise :)..
I’m not sure where you got the impression that they only provide Typescript in their documentation. Have a look at angular.io and you’ll see that they have ES5 as well. But Typescript makes it so much simpler that I cannot recommend enough that you take another look at it before judging.