[WorldMaker]

You can use Parcel or esbuild just on that CJS dependency (rather than as a top-level bundler for your whole project), and then cache the ESM result somewhere. If the package is that old and that unmaintained you can just about cache those ESM builds indefinitely. (That's what Vite kind of does under the hood. That's what snowpack used to do.)

I think npm should probably support doing that at install time.

ESM importing CJS works in Node, mostly, now, but it does have quite a bit of runtime overhead and prebaking it would be good. Especially because it is unlikely to ever see a CJS loader in the browser (and that would be awful if it did exist).