Your last statement sounds very immature, honestly. If you think that what happened between these two was a waste of time, you've got a lot to learn about relationships, and living in general.
i don't see in what it's "immature". from the begining of the story their relationship didn't improve or anything they where friend and dating each over didn't change anything about them or beetwen them. so for me it was really a complete waste of time. things would have been the SAME if they never dated each other. so all this story is king of pointless because NOTHING have really improved or changed.
They very obviously did learn more about the things they like and about relationships in general. She outright says her expectation that sex without love would be terrible was wrong, but she also learns that she personally wants something more romantic. She gains experience that way, both of them do, that they can carry forward into new relationships. And again, they walk out of the experience with a good friend they can confide in that they didn't have before, that's a huge plus in a person's life. Seriously, that's the opposite of a waste of time, which is why I say your outlook is immature. It's simplistic and defining "gain" as only "had a successful romance". That's an attitude that discards quite a lot in search of an ideal and causes a person to miss very valuable things along the way that maybe aren't so perfect.
If they hadn't dated, it's not even sure that they would have gotten to be friends at all, let alone close, lasting friends, which is shown by the fact that they'd clearly been club-mates for a while and not become friends until the dating thing came up.