There is no definition that matches how you are using the word. You just pulled it out of your ass when you said the dictionary defined it your way, and now you are backing off because you were proven wrong. When people say "casual" they aren't referring to mythic raiders. You just want to redefine the word so that you can define yourself into being correct rather than having to make coherent arguments.
They pay the same monthly fee you do, and no amount of whiny narcissism is going to change the fact that there are many times more casual players than mythic raiders. The game should be designed for the average person, not for you and your cute little niche activity. The game shouldn't be designed for any fringe activity, whether that activity is mythic raids or pet battles, two things which are equally important to the core of the game. You aren't special. You aren't more important than anything. The health of the game does not rest on you. Your self-importance does not equate to actual importance.Very well beyond what I can fleece from them what value do casuals have with this conversation? If they will just do whatever randomly why would anyone care to design a system around them? In all likely hood they will simply wholesale copy whatever the "good" players do and then enforce strange rigid requirements on their fellows.
Whatever system is made they have a more parasitic existence simply copying whatever the better players are doing.