WASM is currently indeed bottlenecked on the lack of GC. This is being worked on. I expect a lot of progress over the next two years that will gradually remove most of the obstacles on this and other fronts. None of these are fundamental issues; it's just a matter of things not being perfect yet. Despite this, there's already a lot of early adoption. But I agree that Kotlin on WASM is short term not ideal. In the same way C#/Blazor currently only makes sense for enterprise application where download size is less of a concern. Rust does not really need GC, which is why is a popular language for this already.
As far as bloat is concerned; react is actually pretty horrible. I've seen simple react applications go over 1 MB for no good reason. I'd say the react ecosystem is actually a main driver for people wanting to have some alternatives. I actually prefer more lean approaches. Vue.js seems nice and I'm aware of a few nice lightweight dom abstractions (e.g. redom is nice).
