Flutter currently has 2 ways to run something on the web: 1. CanvasKit. Primarily, this uses webgl. Though, the app has to download a kind of webGl runtime on the first launch, iirc. If the browser does not support openGl, it will use Skia with a Canvas frontend, leading to blurry and poor performance results 2. webRender. This is flutter's way of trying to make a HTML DOM, but its not that great either. It's inconsistent with the rest of the flutter implementations, and has performance issues because it's not really mature/optimized and has a virtual Dom.
I think an exciting use case would be something like 1. Instead of the blurry image and bad performance of canvas redrawing, it might try to manipulate an SVG in the browser. This is pure speculation tho, correct me if I'm wrong.