I totally agree on reinventing the wheel. I think our biggest tool towards that will be Node-API, which is the one low-level building block that JavaScript runtimes seem to agree on (and heck, I'm sure non-JavaScript engines could implement a decent chunk of Node-API). The Hermes team are currently interested in it (https://github.com/facebook/hermes/pull/1377#issuecomment-29...) for implementing heavy chunks of the ECMAScript spec like Intl and Temporal as plug-in features.
It's interesting that you bring up tooling like npm and Cargo, I've never thought of sharing those. Although I'm no great shakes at Rust, I really, really liked how Cargo did things (e.g. optional dependencies and rigid library structure) and it'd be incredible to have that for the JavaScript ecosystem.
Also do keep hearing nothing but great things about Graal, I think it's being slept on.
FYI: https://thenewstack.io/vites-creator-on-a-unified-javascript...
They'll have a tough job getting sticky ecosystems like React Native to adopt, but hope to see them make a compelling case for their stack.
One of the regrettable quirks of our industry is the way we replicate theoretically language-neutral components separately in multiple language ecosystems and verticals. I wish we didn't a separate npm and cargo. I wish the polyglot runtimes you mention (especially Graal) would see more adoption. I wish we didn't have both Duktape and MicroPython. There's nothing language-specific about efficient garbage collection or compact bytecode or package dependency resolution.