I believe that you have to have some kind of complexity in an RPG to get people interested in it at the start, but not having too much to lose people in the middle or extremely pissed off at the end. Yes, there is the whole "It's the journey, not the destination" zen crap you can throw, but would you really accept that line if the ending turned out to make just about everything you did completely moot or raise more questions and answers nothing that was raised before or even retcon various things that were clearly established before? If a game is too complex in it's plot, you lose fans and players, but if it's too simple, you also have the potential to lose fans and players because the story isn't that engaging. True, simple stories can work out, such as the Mario and Luigi series, but RPGs isn't exactly Nintendo's forte now, is it? All they really have under their belts would be the M&L and Paper Mario games that have any kind of complexity (because you can't count Pokemon since there's basically no plot and you're only playing to see new 'mons to throw around in balls).
Not only that, but the twists and whatnot are what help define a series or game from the rest of the bunch. Imagine if that instead of a complex break-out (that I would say started sometime in the SNES era and took a huge leap into it in the PS1 era) that all RPGs were just 'random group saves the world without establishing just who they are and what they're fighting' ala Final Fantasy 1. FF1 is really just about four people who go around beating up villains because destiny said so. FF2 is also on the same boat, just on a different end since it's about three people who constantly get a four guy who go around beating up villains because the bad guys are dicks. FF3 is about four people who go around repeating FF1's plot just with different villains, and Dragon Warrior/Quest kinda took the same route as FF2. However, like it or not, in FF4 things started to change. The idea of having the good guy start out on the villain's side occurred and was played around with after that, Chrono Trigger had the idea of using time travel as a way to create complexity and one of the first multi-ender games created, Shin Megami and it's use of demons as allies and going up against God, and god knows what other SNES era RPGs I'm missing that did something different. Then we hit the PS1 era with FF7, 8, Legend of Dragoon, and various others, and then the PS2 with Disgaea, Kingdom Hearts, and a whole tidal wave full of other titles. They're all complex in their own way to tell a story, it's just whether or not it was good that is the question.