I wonder if graffiti critique is a thing. Like art (or anything), most graffiti is unremarkable, boring, badly done and forgettable. But even a tag can be well done, fun or interesting in other ways.
[1] https://www.reddit.com/r/graffhelp/
[2] https://www.reddit.com/r/Bombing/ (a good example of what "good" graffiti, as defined by the graffiti community, looks like)