It's also misapplied here. If anything, it appears from the changes being made to WebKit that the issue is detailed interactions with DOM change logic and with CSS, not JavaScript. JavaScript may tickle the issue, but that's like blaming the mouse for allowing you to click on a button that has expensive operations attached to it.
I've definitely managed to make a page that uses almost no JavaScript and is dog-slow on Firefox (until Mozilla updated the rendering engine) just by building a table out of flexboxes. There's plenty of places for browsers to chug and die in the increasingly-complicated standard they adhere to.