OoT was definitely not selling out. The Zelda series has a serious storyline in which there are serious consequences to Link's actions. In OoT, you basically open the door for Ganondorf so he can rule the world while Link sleeps for 7 years.
Even in WW, the storyline was very serious, despite the graphics being cel-shaded. I think Zelda is and always has been its own game for so long that there's nothing it could do to "sell out", short of giving Link a gun.