No, because there is generally not really any benefit to your games. There are one or two cherry-picked features that are used when supported if they might bring some kind of performance benefit, but ES6 features are in general just a bunch of useful tools for JS programmers. There is also a major downside that using the latest JS features will break compatibility with old browsers (such as IE9-11 and many old Android devices). That can be worked around using transpilers, but given they may impose a performance impact and can be a source of extremely difficult bugs, I'd rather just keep using ES5.