Gatekeeping is trying to keep specific people out of a particular group or experience based on arbitrary, unimportant rules that the gatekeeper made up in their own mind. Like saying girls can't play with trucks because no penis or saying "if you like (x) musical artist, you're not a real fan of (x) musical genre". If you want a more denotative definition, it's the person that opens and closes the gate, and I see neither gates nor people keeping them in this picture.