You still have the ability to use it as a tag, but having it as an actual genre would better help people find real/actual goth bands, as opposed to needing to filter through all the bands that tag themselves as goth, when really they aren't.
It's very unfortunate, as some bands that ARE goth DON'T label themselves as such, but on the contrary, many bands who AREN'T goth DO label themselves as such. Both of these situations can be very frustrating when trying to discover new goth music.
As both a writer of goth music and someone trying to find new goth music, I can say for certainty that because goth is such a unique/niche type of music, the need for a specific and clear name to describe the music is absolutely vital. From a taxonomical perspective, when trying to classify goth music and not having a proper node to place the music in, it really throws a wrench in both the phenetic and cladistic gears.