Further, as I've pointed out to you before, the CLR does not really support unmodified C and C++ as well as WebAssembly does. It supports C++/CLI instead, which is not a superset of standard C or C++. And worse, the main (only??) compiler for C++/CLI has no plans for keeping newer features of C++ working on the CLR.
In the context of this discussion about integrating GC into a VM that supports C and C++, the CLR is an odd choice of example anyway. The CLR doesn't aim to support existing languages unmodified, every port I've seen has been similar to C++/CLI in diverging from its original definition, specifically because of its memory and object models. And those are precisely what WebAssembly does away with.
What do you call emscripten and the language extensions it makes use of, then?
One of the major features for .NET Core 3.0 was C++/CLI support. It is a major .NET language in Windows desktop applications, as it is more convenient than writing P/Invoke annotations.
Also CLR is just the example more people nowadays can relate to, I can give other C and C++ bytecode examples.
.NET Core 3.0's C++/CLI support, again, is not standard C++ and never will be! It's just the same C++/CLI on a more up-to-date CLR.
(Things may have been better in the past, but the C++/CLI spec has not kept up with the C++ standard at all and so the main implementation, when asked for "C++17 and C++/CLI," just kind of shrugs and makes a mess.)
This is not true of emscripten. It does add some Javascript binding functionality, but that's no different from e.g. Linux or Windows offering their own platform APIs beyond the C++ standard library. You can just take a lot of pre-existing standard C++ programs, often including those that use platform-specific APIs, and drop it in emscripten!
Bytecode for C and C++, is even older than the CLR, and before the browsers, there were a couple of J2ME competing stacks that used C and C++ instead.
The innovative thing with wasm is half political (that is it is socially free to implement and use) and half the lightweight reliable sandboxing.
It is perfectly possible that there is a subset of the CLR that would have been a better Web-Assembly than this WebAssembly, but the CLR chose different trade-offs so it isn't.
One of WebAssembly main distinguishing features is that it can compete with eBPF in term of safe embeddability.
But WebAssembly (wasm32) code density is not the world's best. Comparing to good old x64 it goes at 1.42/1.0 ratio which is still tolerable. I hope someday we'll get a more dense instruction set like ARM's Thumb.