It’s a great game, but it’s hard to argue that it didn’t change the genre, and all of multiplayer video games, for the worse. Multiplayer games can no longer be designed to just be fun. They must also be addictive, they must retain players, they must keep them coming back, etc. using every manipulative trick in the book like XP bars and unlocks. You might say MMORPGs did this first, but this was the application of that feedback loop to a competitive action game.