Comment by keerthiko

As @veridies says, the point of Light's actions in DN is to make the world aware of him as a God. His objective is not merely to have people die, but to let the world know that there exists an entity that is "doing good" and passing righteous judgment, living amongst them and aware of them.

If you consider that a core objective, besides just weeding out criminals, his moves weren't "middle schooler mistakes". It is explicitly addressed in both the show and the manga that he intentionally creates patterns and responds directly to provocations to make L and the detectives aware that he is amongst them and is challenging them. Whether that's a merit-worthy core objective or not is questionable, but to him the whole Death Note would have been meaningless without the ability to parade as a God, and that's what made the plot interesting.