> If we still need to target es5 4 years later You don't. Unless you care about IE11 (for most consumer products and mobile apps isn't necessary) you can use m

> If we still need to target es5 4 years later You don't. Unless you care about IE11 (for most consumer products and mobile apps isn't necessary) you can use many of the features up through ES2016 or later without transpilation. My business uses JS classes, arrow and async functions, and new prototype methods without issue.