Hmmm...your definition of "fun" is a little limited, merten.
"Fun" to some people is being flogged with a whip. In fact they have so much fun they tend to... well, you know where this is going.
Perhaps it might more closely fit your definition if the phrase were to be changed to "The purpose of role playing is to enjoy oneself". It may be excrutiating agony, but if you can look back on it with pleasure, then you enjoyed yourself...in other words, you had fun.
My take is that roleplaying is an excuse for a social gathering of your friends and for everyone to enjoy themselves. If that's exploring a dark dimension that is unlike your own nature, or just revelling in being included in a close-nit group (either in reality, or in game), or as you put it, experiencing something, then the objective or purpose has been accomplished.
One of the things that makes role playing enjoyable for me as a player is that I get the opportunity to watch a fictional character that I've created grow as a "person", become more complex and eventually reach a stage where I can no longer play them, because they have become a distinct personality. They they appear from out of the back-story of the campaign usually in some subtle but powerful way, and occassionally, they get taken for a spin in a full-blown adventure.
I've got PCs that are 15 years old, have grown, aged, married, had children, built houses, become businessmen, or even powerful behind-the-scenes manipulators. All through, they've grown and advanced in skills, and in personality. That is, they've become more real. Hell, half of them have e-mail addresses; real ones!
One's even a member of this forum!
(He hardly evey logs in, though. But I guess when you have two wives, and five kids, you get to be kinda busy with other stuff.
Internal consistency is an absolutely critical factor for me, too. It's the prime ingredient in the "suspension of disbelief" that is such a necessary part of any successful entertainment, whether it be an RPG campaign, a book, a movie or TV show, or a play. If you come up against something that makes you go "Huh? Wait a minute; that doesn't make sense!", then for you, the entertainment is marred, because you are no longer immersed in the story. Dragons flying about breathing fire may make no sense when viewed externally, but within the context of a fantasy story, they are such an integral part that you accept them. But if the fantasy environment has a huge, ancient dragon inside a hall with a single man-sized door as the only exit, you are suddenly brought up against something that doesn't make sense within the context:
"What does it eat to stay alive?? Surely not wandering denizens, since they'd all have been eaten years ago, or learned to avoid this place."
"How did it get here? Where's all the dragon dung?....."
Is it really worth all the fuss about the facts when the point is to have fun? Is it worth carving a complex character when you in a sense see the world in more detail than the GM?
As a player, you sometimes have to give the GM some elbow room to learn the environment. If you are going to play for the first time in ages, it's going to take some effort on your part to stop you from trying to take over if the GM does things differently to the way you would.
But if you want to keep this person's friendship, you will have to back off, and let them do things their way. As for carving out a complex character, I do that for my own pleasure. I really don't care if the GM appreciates all the hard work I put into the player's back-story and history, because I do it for my own pleasure. But it's also a perfect opportunity for you to create story hooks for the GM to hang an adventure on that involves your PC.
I don't know how many times a chance comment or sentence in a PC's background has been used for a multi-session adventure of epic proporations in our group. And all because I and my friends enjoy creating complex, detailed PCs with extended histories, and lots of quirks and foibles.