I agreed with you until I had to be wary of performance on mobile devices where the user may have to pay 10s of milliseconds just on boot per every 15kb of java

I agreed with you until I had to be wary of performance on mobile devices where the user may have to pay 10s of milliseconds just on boot per every 15kb of javascript you add. At the end of the day you ask yourself "do I really need to add 34kb for 'for..of' or can I get away with a small concession?" like the blog post asked. You may find that it might not cost you much to pay attention to your trade-offs.