Hi BlackoutCrisis,
The engine is not what determines how large of a game you can make. That is reliant on your hardware, server size, etc. You can absolutely make a large scale game, including MMO’s with UE4, the questions to ask yourself are: Does UE4 fit my needs for programming/mechanics? What style of gameplay am I looking for? Does UE4 have the features I need to be able to make my game? Etc. With UE4, you have the possibility of making pretty much any type of game you want, though some may require C++ or changes to the source code to fit your specific needs. We have a large documentation section that can help get you started and our community of developers tend to like helping new developers out! Unreal Engine 5.1 Documentation | Unreal Engine 5.1 Documentation