I personally think it’s irresponsible. It’s essentially the software engineering equivalent of a surgeon not using a new/better surgery technique because it’s d

I personally think it’s irresponsible. It’s essentially the software engineering equivalent of a surgeon not using a new/better surgery technique because it’s different and not what they’re familiar with. Sure, it’s not life or death but your clients are definitely worse off than if you’d just taken the time to learn ES6. Not knowing ES6 also just makes your life harder if you adopt other new JS advancements. For instance, it’s harder to look at the docs and examples for React and it’s related libraries. It’s harder for you to adopt Flow or TS. Lastly, it should be especially easy for you to pick up ES6 if you know ES5 inside out.