Yes, in browsers, JS animations are still hard (I might even say impossible to do well for large apps with a lot going on). One anecdote: I spent a month trying to build a 60fps scrolling list view in JS from scratch (JS driving all the animations). No matter how hard I tried, I couldn't make it work on the web. I believe it was image decoding interfering but it's difficult to say why. Then I took that same example, which by that point was optimized, and ported it to React Native in a few hours(where we have off-thread image decoding and timers I can trust) and the example was like butter.

Now of course, I had hand optimized the performance, but my point is that on the web, there was nothing I could do, and with React Native, there was something I could do to make animations smooth. This is not to say you should be doing animations in JS, but if you want highly customizable interactions that can be immediately stopped by a touch processed in JS, you should try it out and see how it feels. For things that are "fire and forget", or platform specific, you should try using CoreAnimation/keyframes etc which protects the animation from your business logic.