It was neither a design choice nor a technical limitation. It was a big complicated thing which necessarily involved fiddly internal work and coordination between relatively isolated groups. It got done when someone (Joyee Cheung) actually made the fairly heroic effort to push through all of that.
Joyee has a nice post going into details. Reading this gives a much more accurate picture of why things do and don't happen in big projects like Node: https://joyeecheung.github.io/blog/2024/03/18/require-esm-in...
Node.js made many decisions that have massive impact on ESM adoption. From forcing extensions and dropping index.js to loaders and complicated package.json "exports". In addition to node.js steamrolling everyone, tc39 keep making are idiotic changes to spec like `deffered import` and `with` syntax changes.
Requiring file extensions and not supporting automatic "index" imports was a requirement from Browsers where you can't just scan a file system and people would be rightfully upset if their browser modules sent 4-10 HEAD requests to find the file it was looking for.
"exports" controls in package.json was something package/library authors had been asking for for a long time even under CJS regimes. ESM gets a lot of blame for the complexity of "exports", because ESM packages were required to use it but CJS was allowed to be optional and grandfathered, but most of the complexity in the format was entirely due to CJS complexity and Node trying to support all the "exports" options already in the wild in CJS packages. Because "barrel" modules (modules full of just `export thing from './thing.js'`) are so much easier to write in ESM I've yet to see an ESM-only project with a complicated "exports". ("exports" is allowed to be as simple as the old main field, just an "index.js", which can just be an easily written "barrel" module).
> tc39 keep making are idiotic changes to spec like `deffered import` and `with` syntax changes
I'm holding judgment on deferred imports until I figure out what use cases it solves, but `with` has been a great addition to `import`. I remember the bad old days of crazy string syntaxes embedded in module names in AMD loaders and Webpack (like the bang delimited nonsense of `json!embed!some-file.json` and `postcss!style-loader!css!sass!some-file.scss`) and how hard it was to debug them at times and how much they tied you to very specific file loaders (clogging your AMD config forever, or locking you to specific versions of Webpack for fear of an upgrade breaking your loader stack). Something like `import someJson from 'some-file.json' with { type: 'json', webpackEmbed: true }` is such a huge improvement over that alone. The fact that it is also a single syntax that looks mostly like normal JS objects for other very useful metadata attribute tools like bringing integrity checks to ESM imports without an importmap is also great.
You're right. It wasn't a design choice or technical limitation, but a troubling third thing: certain contributors consistently spreading misinformation about ESM being inherently async (when it's only conditionally async), and creating a hostile environment that “drove contributors away” from ESM work - as the implementer themselves described.
Today, no one will defend ERR_REQUIRE_ESM as good design, but it persisted for 5 years despite working solutions since 2019. The systematic misinformation in docs and discussions combined with the chilling of conversations suggests coordinated resistance (“offline conversations”). I suspect the real reason for why “things do and don’t happen” is competition from Bun/Deno.