3DGS is just great in its features, but the weak point is

WED:
- very difficult to use when placing many models, no workflow, not user friendly at all
- todays levels are levels in which you use models only, so there must be some easy handling for models, appliing predefined materials and shaders and easy lighting system, a preview system (todays pcs are fast enough)
- everything what is used in a game has to be insertable like sounds, scripts, menu system, terrain editor, etc

so everything depends on the access you have got to the engine. The engine itself is not the problem at all, I guess

so WED is the key