If e-sports want to become even semi-mainstream, then they must become accessible. The tops sports in the world are popular because they are accessible. You don't need to be a pro to have fun participating in rec leagues or friendly pickup games.
Popular sports are also easy to understand for casual audiences but strategic/competitive enough for the hardcore crowd. Hell, one of the reasons MOBAs blew up is because it meant people could play an RTS without having to be good at base building and resource management, all they had to worry about was fighting.
I think one thing that gamers need to get over as a whole is this elitist attitude that content/games should only be tuned to the 95 percentile (or whatever percentile they think they're in
).
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Oh course it is an e-sport. If poker can be considered a sport then Hearthstone can be considered an e-sport.