IT is brutal. You either evolve or you die. If JS didn't introduce new features, it would be just replaced with the "next big thing" that introduces things. Arrow functions, classes and promises don't make things more complicated. They are added to make things more readable
I sympathize and resonate with the author. While for me, the JS language features are still manageable. What has outgrown me are the layers upon layers of abstractions used in modern JS app, like React/Redux/... We no longer have a straightforward, plain JS app. To understand the code, we have to 'see through' the thick layers of frameworkds/middleware. Modern JS app is becoming as ugly as J2EE last time used to be.
This really reads like it was written by someone who does not know how React and Redux are used. Both of those libraries are incredibly straightforward and minimal in their functionality — orders of magnitude less complex and multifaceted than something like Hibernate or Spring. When you compare a React app with something written with what JS “used” to be (vanilla JS with browser hacks, jQuery, Backbone) the number of hacks or workarounds per line of code in the React app is much lower in my experience.