That's called OOP, it may looks cumbersome at first, but once you get a hang of it, you'll realize that 3DGS could get more benefits from it.

Yeah, Unity su*ks, especially if you get a hang on 3DGS for a long time. Shadow baking takes forever even on simplest scene. Material importing can(or always) get messy, you need to assign each texture to material and you got no clue "which texture is this material".

I guess Unity3D is really for those designers that want to get their design up and running fast, it's like learning in high school, just follow what your teachers said and you'll graduate. 3DGS in the other hand, is more suitable for those who want to take everything deeper. It's like learning in University, here's the books, here's the classes, do whatever you want, learn whatever you want, if you do it right you'll graduate.