Baking lightmaps or lightmap based GI is fine; but there are situations where there is no possible way to use precomputed data for lighting. Games which generate a level at runtime needs to use dynamic lighting. As far as I know neither UE nor Unity allows access to runtime baking.
Best thing you can do is create the level then combine the static meshes to a single mesh create an atlas send data to external renderer bake and re-import the level, and apply the lightmap. (Which on complex meshes with high poly count can take couple of hours depending on the client computer, not to mention its stupid).
So some game types have different needs and require different methods. Personally I would love to use a fast robust lightmap system which works with generic static meshes, but its not possible at the moment.
By the way I read somewhere they change the directional light rotation at runtime with pre-baked lightmap library. Since the time of the day and the sun position/rotation is pre-determined you can create a bake library and call the right lightmap associated with the light setup.Its not dynamic but can be switched when user enters/exits zones.