Grant was no genius. He looked at his predecessors and their reluctance to "finish the job"; he counted the number of soldiers on both sides and the Union had more.
He slammed against Lee, time after time at a horrible cost. Determined, he was; effective, too.
But a genius, Grant ain't!
If your complaint is about the body count, then compare Lee's body count with that of the Union army when Lee was on the offensive. I think you'll find that Lee's was higher there, too. But that is the price you pay to maintain the upper hand. With Grant constantly attacking he forced Lee to react to him rather than the other way around. An army forced to react rather than act is not going to win, regardless of who is in charge. Lee was never able to gain the initiative over Grant. That wasn't due to bad luck on the part of the confederates, but good generalship on the part of the North.