I don’t agree with that. Yes, chess may have a binary win condition, but playing does not necessarily mean that’s your sole reason for playing.
You could be playing for fun, whether you win or lose.
You could be playing knowing you’re going to lose, but hoping that you’ll learn something from your opponent and become a better player.
You could be playing just to spend some time with the other player.
The point is that saying any game is about having fun is kind of pointless. It’s true, but it doesn't really reveal anything about the game or about the participants.
What else do we get from games? What other goals do they have? These are the questions that will have different answers. Where we actually share and learn.
Saying that there is something beyond fun isn’t an attempt to define successful play for anyone else so much as it’s an invitation for others to share what that may be. Until we do that, no one can understand how play may be successful or unsuccessful for anyone else beyond the very basic “it was fun”.
You can disagree all you want! No worries there.
That said, the specific example was
chess. And I was explaining what I assumed was self-evident; chess (and other, similar, games) are not TTRPGs. In fact, this is such a well-known issue that it is a primary problem that has been experienced since the beginning of TTRPGs when it comes to explaining how they work to people who are used to more traditional styles of play.
Now, moving to your specific issue- people are describing, for other people, the "point" of a game (like D&D) and more particularly stating that the point is (paraphrasing here) "completing missions."
But that's not it. If, instead, it was a practice to speak to the people who are playing the games in question and determining what they are getting from the game ... as opposed to telling them what the point of their game
should be, then it would be more likely that there would be a receptive understanding.
Reiterated another way- yes, people can get "enjoyment" from TTRPGs in multiple ways. There are different methods to enhance their enjoyment that can be discussed. But I have rarely seen people say, "You know what? You're right! I shouldn't pay attention to my own goals, and instead listen to what other people define as successful play for me. Because that ...
sounds like fun."
But I could be wrong on that. I often am! If it's super-important to you, you can discount fun when it comes to TTRPGs as much as you want. As for me, I tend to elevate fun over high-falutin' concepts and words that I don't understand and can't spell.
