That idea of a universal/generic VM supporting many languages has been tried many times, with limited success
What wasm is doing is something different than previous efforts. The gc facilities aren't provided for the sake of interop with other languages, or for the sake of sharing development resources across language runtime implementations. Wasm is providing gc facilities so that managed-memory runtime languages can target wasm environments without suffering on account of limitations imposed by the restrictive memory model, and secondarily to reduce bundle sizes.
Wasm can potentially support more tunable gc parameters to better suit the guest language's idiosyncrasies than can other general purpose language runtimes. And unlike the runtimes we're comparing it against, language implementers don't have to option of making something bespoke.
What wasm is doing is something different than previous efforts. The gc facilities aren't provided for the sake of interop with other languages, or for the sake of sharing development resources across language runtime implementations. Wasm is providing gc facilities so that managed-memory runtime languages can target wasm environments without suffering on account of limitations imposed by the restrictive memory model, and secondarily to reduce bundle sizes.
Wasm can potentially support more tunable gc parameters to better suit the guest language's idiosyncrasies than can other general purpose language runtimes. And unlike the runtimes we're comparing it against, language implementers don't have to option of making something bespoke.