Ursula K Le Guin said, when talking about fantasy literature in her seminal essay, "Why Are Americans Afraid of Dragons?", that the primary "use of the imagination" is "to give you pleasure and delight." She added a secondary use, which is "to deepen your understanding of your world, and your fellow men, and your own feelings, and your destiny."
But let us not skip over that she said that the first is primary. This was part of her defense for fantasy at a time when it was still deemed in a pejorative light, as "mere escapism." Her view was that giving pleasure and delight is itself a noble cause.
But in terms of D&D, we play it to have fun, to experience pleasure and delight - and that is shared by everyone. Anything after that point varies on the individual. In other words, what meaning they ascribe to the game--and to what degree--is entirely up to them.
I personally don't go to D&D for Le Guin's secondary use, or at least only to a very small degree. I might go to that in a book or film, or when writing a story--it is a good way to work out an idea. But for D&D? No, it is just about fun: playing make-believe in an imaginary world.
This is not to say that it is wrong for another to find that secondary use - not at all. For some people, D&D is the main context they have for being imaginative and creative. Nothing wrong with that, at all.
I think a lot of the disagreements on this meta-topic have to do with the different degrees to which people apply Le Guin's secondary use, and more specifically, what lens of interpretation they use. And depending upon the latter, what hermeneutics one employs, different aspects of D&D will look differently.