I've seen Svelte used in a number of high impact tools, including in AAA videogame UI. In my experience, I've seen engineers very happy working with it, and it meets the performance needs for a videogame it should be good enough for the web.
elaborate, please, because this sounds so bizarre.
Are they bundling an entire web view and then interfacing it with their game engine? Not only is the tech conceptually weird, I can't think of too many AAA games that have very complex UIs other than maybe the CK series.
The interface between the game engine was designed to be as decoupled as possible. The UI could run in a browser with a mocked game underneath it, which allowed the UI devs to iterate very quickly. This also has the advantage of allowing UI to be built before the game had a feature implemented.