I guess I’m jumping to conclusions but it seems like a lot of lessons have been learnt since JVMs and .NET came onto the scene, and that WASM runtimes and the future languages that target them will prioritise speed at every stage.

Go already cross-compiles to WASM, so if desired, Go code can be run via WASM. But on the server, you probably rather want to run the Go code natively. For the client, this should be quite interesting.

One doesn't just write WASM though.. WASM is like the JVM. You still need to write code in some other language.

Exactly. Hence posing the question (rhetorically, I suppose).