I think typical ES6 code is actually less likely to use parts of JavaScript that are difficult to optimize because we now have a lot of features that let us be

I think typical ES6 code is actually less likely to use parts of JavaScript that are difficult to optimize because we now have a lot of features that let us be more clear about our intentions. Proxy objects are probably more difficult to deal with, but the rest of ES6 is probably easy to take advantage of.