Why is the volume fog formed by texture projection ineffective

Why does the use of colored texture maps for light function not work for volume fog, and even the shape of the projected texture map for volume fog is lost? If there are problems with upgraded new features, it’s not a big deal. Why do some old features often fail, wasting users a lot of time looking for the cause? Why do these low-level errors always occur? It’s really infuriating,,,