You have a lot of browser support.
You have tail call optimization.
You have import statements.
Lamba’s are pretty amazing.
Immutable and block scoping objects with “const” and “let”.
Classes and OO Inheritance.
Functors, and all that functional goodness.
String templates that handle interpolation for you.
It doesn’t have everything that ES6 has.
It doesn’t have all the support that ES5 has, but you can always transpile your ES6 code.