I want to say I think they are talking about how great it would be if we could kick JavaScript to the curb and just use WASM for everything. I’m kind of in the same boat.
However, WASM currently doesn’t have direct access to things like the DOM, if I recall correctly (this might be the guardrails the OP was referring to?). So, it’s only really good for things that are heavy on the CPU. But, as a counterpoint, I don’t think it’s from a lack of effort from anyone’s point. The last thing I remember reading was that there were still a lot of things being worked on to make it happen.
Quick Perplexity search:
There are proposals and efforts underway to allow WASM to eventually call DOM APIs directly, without going through JavaScript. The main one is the “Interface Types” proposal which would allow WASM to bind to Web IDL interfaces.
Another related proposal is WASM GC (garbage collection) which was announced at Google IO 2023. This will allow WASM to share the same managed heap as JavaScript.
As a wise person once told the Internet, don’t worry about picking the best one. But if you really had to pick one just start with the rust book. https://doc.rust-lang.org/book/ I would suggest to just dive in with a specific need you want to solve and instead of using your language of choice just use rust and look up stuff as you go. Hands on learning is usually the best learning. The only thing you need to “learn” is how to follow the ownership/borrowing paradigm that rust brings to the table.