Well, 18.44 shows the duty of a Shoodra is service. This should make one infer that this is distilled wisdom and not word of God.
Yet, 18.36 shows people of so and so Gunas are inclined to so and so activities. But the description of being a Shoodra won’t match everyone. In that case, this varna system is not described to be birth based, and secondly, the classification only works as long as it exists. If the society does not have Shoodras, then there is no such people whose duty is service.
Also, 18.59-60 says your own nature will drive you to do what you were meant to do. So these boxes are not worth focusing on, compared to the broader message. The boxes may have been useful in an older time, and dialectical materialism would’ve overrun them by now.
Also, 18.41 says that it is one’s Gunas that determine their Varna.
So well, I can consider it the word of God under these conditions.