If I may - this is not a babylon issue. This is an issue with understanding how typescript is working and how import is working, and how es6 is working, and how npm is working. And how webpack is working. And how to combine them all. Notice that I asked - what is the error you get during the build process. What do you get when you are actually trying to compile the project.
Here is my recommendation. You can take it or leave it. You are trying to jump head down into a very deep pool from the 10m board (again - all of these are not (!) babylon related). Try jumping from the 3 meters (or maybe the 1 meter) and master it. Try a webpack project with javascript only. Understand how import works. Understand how webpack loaders work. Then move to es6. Understand how tree shaking works. Understand how javascript modules are loaded. Move to typescript. Understand what the different tsconfig parameters are doing, and why the heck can’t you manage to compile. We’ve all been there. I still am too!
The project I linked before is a ready-to-use project, with everything you need. But you insist on using different methods, and wonder why they don’t work, even when we explain it.
I created the linked project exactly for that reason - there was a confusion as to how to use the latest and greatest, how to combine all of those goodies the web offer us into one working project.
A 7 years old project, being used on production websites all over the web is mature. Or at least this is my opinion.