Baseline ES6 been supported for many years now.

There are very few things a transpiler will do for you today. Some critical langauge features are completely impossible to substitite, or emulate. Given this, what's the point?

The few non-critical features can be more reliably polyfilled manually than relying on transpiler which will mangle the rest of your code which has nothing to do with that function, and with 50/50 chance to introduce own problems.