WASM has become a Web Standard a couple of years ago. It's very simple (at its first version at least) which allowed all browser implementers to support it from day one. It has accomplished the goal of running C/C++ applications efficiently. Rust code can mostly compile to WASM and run as well (only crates that use stuff like drivers or OS-specific calls don't work).
However, a few years later, there's not much that has been improved in the WASM world. The work being done on the current proposals is monumental and would require the same level of investment that has already been spent on things like the JVM and the .NET runtime, as you point out. To write a specification as well written as WASM for these things is basically impossible.
And they're only doing that in order to support other high level languages to compile to it without having to ship their own runtimes.
But the problem is that given how hard the work is, the benefit of doing this would need to be enormous to justify spending so much work on it... but it's not! JavaScript, for better or worse, has pretty decent performance and a huge amount of code has been written in it. If you try to re-write something in Java or Go, say, to replace JS, even when WASM supports GC and exceptions, I doubt it'll improve anything over JS performance.
Besides, GraalVM already exists which can run nearly any language with very high performance if you're not completely locked on the web platform.
So, all this drama that's going on around WASM for what?
I say, leave it alone, make sure it stays simple and supports high performance stuff written on non-managed languages... and consider the job done.
However, a few years later, there's not much that has been improved in the WASM world. The work being done on the current proposals is monumental and would require the same level of investment that has already been spent on things like the JVM and the .NET runtime, as you point out. To write a specification as well written as WASM for these things is basically impossible.
And they're only doing that in order to support other high level languages to compile to it without having to ship their own runtimes.
But the problem is that given how hard the work is, the benefit of doing this would need to be enormous to justify spending so much work on it... but it's not! JavaScript, for better or worse, has pretty decent performance and a huge amount of code has been written in it. If you try to re-write something in Java or Go, say, to replace JS, even when WASM supports GC and exceptions, I doubt it'll improve anything over JS performance.
Besides, GraalVM already exists which can run nearly any language with very high performance if you're not completely locked on the web platform.
So, all this drama that's going on around WASM for what?
I say, leave it alone, make sure it stays simple and supports high performance stuff written on non-managed languages... and consider the job done.