It's an extremely bad idea to go and build from scratch a do-everything game engine with AAA 3D capabilities, but there is absolutely space for engines with a v

It's an extremely bad idea to go and build from scratch a do-everything game engine with AAA 3D capabilities, but there is absolutely space for engines with a very specific focus. If you want to make a VN, would you rather open up a blank project in Unity or just use Ren'Py? In the commercial space, RPG Maker and GameMaker continue to exist.