//One or more exports ✔️ export * from filename.js
There is nothing more simple than one or more export statements in an index.js file that define a known ECMA module. Need more than one module for separation of concerns? Just create another index.js file in another folder.
The ngModule system is legacy and just needs to be changed. Some may argue in favor of it, for them the feature should stay as is. For others, that prefer the other way, a simple option should be allowed for every new Component, Directive, Service etc. Instead of specifying an NgModule we should be able to pick an index.js file.
I opened a ticket to Angular on the subject and see other's have too.
JWP2020 Allow Index.ts files in NgModule System.