Yeah, there has never been a case of software breaking out of a sandbox or VM.
Fact is it allows running native x86 code downloaded from the internet, it's orders of magnitude more dangerous than e.g. Javascript running inside a sandboxed runtime.
I'm not sure why you're trying to say ? Two wrongs make a right ?
For the record: I think that JS is a horrible idea too. What happened to the old rule of thumb that once you let someone else run their own code on your machine you should consider it compromised ?
Depending on your requirements, it can be really easy to sandbox code. I could write a simple virtual machine in an hour or two that's more secure than your typical jpeg decoder. So it's really worth looking at exactly what kind of sandboxing and complexity is involved.
Regardless, it's pretty much already been killed. Too bad it's taken 8 years for a web standard (WebAssembly) to match it.