[joepie91_]

It's a fundamental technical constraint of any tool-less setup. At some point you need to traverse the dependency tree by parsing modules and following imports, and your choice is to do that either:

1) on the client, across the network, one roundtrip for every level of depth, or 2) in a build environment, directly on the filesystem

Option 2 means you need some kind of build tool to make it work, and by that point it doesn't really matter anymore whether the tool just traverses the dependencies and makes a list of filenames, or also concatenates their contents into a bundle.

And that is why the fundamental premise of ESM cannot work; there are no technical options besides those two. If you want to avoid network roundtrips, you must have build tooling. No way around it.