I don't think that there is anything wrong with this track being too simple. People always try and add this and that, just for the sake of doing it, or because they can. You need to remember that the most important track will be the rapping. To much rap music lately is too busy, and the rap is not at the fore front. But if you listen to eminem or Dr. Dre. The rap is always forfront, and while the beats have stuff going on, they never forget what the track is about, the rapping.
It's good to mix things up on a rap album, and a straight forward not to busy beat really will change the focus. And once there is rap on this track, it will be quite filled out. Zellus has done a good job focusing.