Sometimes the irregular undulations of a yard's surface are beneficial. As in, possibly discouraging draining water into your basement, or providing a berm for sound abatement. Some gardeners would prefer to garden on hills, some would prefer trenching, depending on your local conditions.
If you have a lot of trees, changing the level of the soil they are using could kill or hurt the trees.
It's all pretty variable. For all I know you have some mole tunnels and a few areas of compaction that need amendment. That's easy enough to handle.