As in a Platinum ranked player in the competitive ladder. Could apply to either Overwatch or Starcraft. Plat players fall into the "slightly above average" skill level, and tend to be the butt of a lot of jokes in competitive communities.
i may be an idiot but the joke makes no sense given his dick size
Well, just big dick isn't enough. It require quite a skill to be pleasurable for both parties and needs a lot of blood to keep it hard, meaning that a man will dry up and exhaust quickly.