Part of the problem here is that the entire JS ecosystem is built around local copies of things, so there might not be a lot of institutional knowledge in that

Part of the problem here is that the entire JS ecosystem is built around local copies of things, so there might not be a lot of institutional knowledge in that corner of OSS to pull off the "shared env" thing quite well. That plus scarring from browser differences over N years. Of course it's still totally possible, but there are probably gotchas that aren't obvious if you're mainly a web developer.