See: Suggestion: You should be able to load module-scripts in the file:// protocol.
I believe JavaScript modules should be allowed in the file: protocol because they allow code to be... modular.
It is very helpful, and, in some cases, important, to split code up into smaller units which later come together as a whole.
Unfortunately, in the file: protocol, where a lot of a newcoming web-developers will be experimenting with stuff, JavaScript modules aren't allowed (due to a CORS error).
I myself have faced this problem where I wanted to use modules, but I had to suck it up and put everything in one file.
In addition to my own account, there are other people who have commented on my Issue that share the same sentiment.
Thank you for reading; I hope I will see some support for this suggestion.
Cheers.