What drove me crazy is that for the longest time, people dismissed the fact that there were issues when using CSS at scale. The response was along the lines of "look, I'm using Sass and now everything is magically working great". What I wanted from that talk is to get people to admit that there were real issues and start working on solutions for them. On this front, I think it worked way better than anticipated!
As for your original question, I honestly don't know if writing styles in JavaScript is the best thing to do and even that is a wide space, there are so many ways to do it. But people are trying a lot of different things and it's super exciting to see!
PS: there's still is this accepted stance that setting styles inline from JavaScript is slower than using CSS. I can't find any reasonable argument why that would be the case. If you set the style directly to the element, it MUST be faster: the browser doesn't have to match that element against the thousand of CSS rules you have, doesn't have to invalidate cache when you add/remove rules or move elements around. But yet, I somehow can't convince people that my argument is reasonable and to get people to write benchmark about it / get browser vendors to actually make it faster if that's not the case already.