It's not just about string performance, it's about making wasm a first class experience on the web. That includes performance improvements - because you don't need to wake up the js engine - but it's a lot more than that. Including much better dev-ex, which is not great as you can see in the OP.
It would also enable combining different languages with high-level interfaces rather than having to drop down to c-style interfaces for everything.
The c-style interface of wasm is pretty limiting when designing higher level interfaces, which is why wasn-bindgen is required in the first place.
Luckily, Firefox is pushing an early proposal to expose all the web apis directly to wasm through a higher level interface based on the wasm component-model proposal.
> Comparing today's internet to the 90s is hardly fair. It has become extremely predatory...
I think you're missing the point they're trying to make. It's not that the problem isn't real, it's that the solution won't work. Kids will find a way around. They have a lot more free time than us.
Modern languages come with lots of interesting features like better dev ex, null safety, etc.
Js is a fine language, but there are other languages that bring unique advantages, the web shouldn't block developers from using better tools.
The web is best off when developers have freedom.