What's the point of glycolysis in fermentation? In order to initiate glycolysis, 2 ATP are necessary. In the glycolytic process, you generate an additional 4 ATP, which results in a net gain of 2 ATP. If you don't undergo glycolysis, however, then you have an extra 2 ATP not being used. If you do glycolysis, you still got only 2 ATP. Am I missing something here?

Suppose the cellular pool has $x$ATP before starting glycolysis. In the initial phosphorylation steps, we use up two ATP to get the total tally at $(x-2)$ATP. The following steps yields $4$ ATP which brings the final total to $(x+2)$ATP.
Assuming the cell is performing fermentation, the two additional $NADH$ formed will not be contributing to any ATP gain. And hence we _earn a total of $2$ ATP in excess of the already existing amount_.