It heavily depends on what you want to achieve. If the game can be created within existing engines, and you are sure about this, you should use them. For exampl

It heavily depends on what you want to achieve. If the game can be created within existing engines, and you are sure about this, you should use them. For example, if it's just a FPS. If your game requires some special features (for example, creating minecraft withing unity/unreal isn't a good idea), requires performance unattainable by existing engines (you can optimize code just for your cases). This is a classic build vs buy choice.