The danger of not following Jehovah is that they shall lie down in sorrow. Jehovah declares how this happens. Rather than walking in the light of his commandments, his people walk in darkness. However, this is a special kind of darkness. There are those who attempt their own enlightenment. They do not produce true light, but only sparks, only brief and incomplete light. Jehovah tells those who trust in their own wisdom to walk in that wisdom, but that it will not be sufficient to save.
In the New World, the most probable likening of these verses would be to the intrusion of some of the elements of their previous pagan religion beginning to seep into Jehovah’s religion and religious practice. The process of syncretization is when two different systems, in this case religious systems, come in contact and the result is a merging of ideas from both to create new forms. Thus, in the New World, the previous religion would have been seen as the fire that their wise men and women had lit, but which was only sparks of light compared to the gospel.
Isaiah, and now Jacob, warn the children of Israel against these influences of the wisdom, or the world, rather than a faithful reliance upon Jehovah’s teachings.