But you can already do this with DLLs or with SOs files. You can keep your network logic for example inside another module (perhaps the host app) and then load the logic that acts on the received data as a dll.
Process separation and IPC natively using a library such as Qt is literally a few hundred lines of code.
But that's sort of moving the goal posts now. Original claim for WASM was that it allows hot reloading. Which is a thing you can do with DLLs just fine.
No, the original claim of Wasm definitely isn't only one side point about development. The original claim of Wasm is that all of these features are packaged in a well thought out whole + the success of this platform (thanks to browsers mostly) is what's so interesting about it.
It is also hard to contain the DLL/SO, every system has different mechanisms to ensure it can not access 'everything'. Wasm, as build for the browser, has it in its DNA.
Process separation and IPC natively using a library such as Qt is literally a few hundred lines of code.