In AD&D or Basic D&D, the decision to choose class (and race, where that is separate from class) is very often more important than decision made in actual play. And it utterly conditions those decisions (eg whether and how I decide to fight or search or move down a corridor will be conditioned by my choice of class and race, and consequences that this has for equipment, abilities etc).When decisions made during the build process become more important than the ones made in actual play the rules have become the game.