I agree with @Fezter's answer. It looks like many cartography-tagged posts are indeed related to cartography, especially design aesthetics and how to visualize maps in traditional but also revolutionary ways.
This is Britannica's definition:
The art and science of graphically representing a geographical area, usually on a flat surface such as a map or chart. It may involve the superimposition of political, cultural, or other nongeographical divisions onto the representation of a geographical area.
Therefore, I think art and science — projecting maps, graphically representing an area, visualizing data, etc. — are two important elements in cartography and should somehow be included in this tag.
Projections would be related to cartography, yet has its own tag(s). Based on this example, maybe there could be a suggestion for question askers to include more specific tags such as projection. I believe the cartography tag can still be used as-is, but more specific tags should be included as well. On my geography blog (GeoFact of the Day), most but not all posts fit in my large GeoFact of the Day tag category. Each GeoFact of the Day-tagged post also includes at least one specific tag. I think this is an reasonable example of how there can be a large category, which ideally includes more specific categories.
Here's my tag description suggestion:
The study and practice of creating maps (mapmaking) and graphically representing geographic areas with the use of artistic and scientific principles.
It is sort of a mouthful, yet still shows cartography as an overarching concept.