It very possible to make lightning-fast React web UIs. DOM sucks, but modern computers are insanely fast, and browsers, insanely optimized. It is also very possible to make sluggish-feeling Qt or Swing applications; I've seen a number.
It mostly takes some thinking about immediate reaction, about "negligibly short" operations introducing non-negligible, noticeable delays. Anything not related to rendering should be made async, and even that should be made as fast as possible. This is to say nothing of avoiding reflows, repeated redraws, etc.
In short, sloppy GUI code feels sluggish, no matter what tools you use.
For most apps React is never going to be an issue when it comes to performance, unless you use it wrong or you use it for something that is not standard, like rendering fractals. It makes sense to analyse performance if your website is meant to reach absolutely everyone, like old smartphones. There's the issue that a single-page app can be bloated from the start, but that's also in the using it wrong category
> modern computers are insanely fast, and browsers, insanely optimized.
You made the reverse point: If you need modern hardware to run a react app with the same performance as a svelte/vue/solid app on low-hardware, something is fundamentally wrong.
> Anything not related to rendering should be made async,
The thing with DOM interaction is that if you try to make it synchronous then it gets really fucking slow (reflow and friends). So you want it linearized for sanity reasons, but probably not sync.
Not everyone can afford the “modern computers” you are talking about.
This is the first sane comment in this entire comment section. So much nonsense in here, but I guess I should expect that when JavaScript is in the post title.
> but modern computers are insanely fast, and browsers, insanely optimized
I think these facts have been used as excuses to shit up the app layer with slow mal-optimized js code.
An example of a recent high performance app is figma, which blows normal js only apps out of the water. And it does so by using c++ wasm/webGPU for its more domanding parts, which is most of it
I think we have to let go of the "just get more ram" approach and start optimizing webapp code like figma does