The ideal game is somewhere in the middle where the designer focuses on mechanics which combine to produce more than their sum, and then anchor it in handcrafted content meant to show the best angle of the mechanical emergence.
One way to split the hair would be to say the mechanics are procedural (I would rather reach for the programming metaphor of composition, however) while the environments are hand crafted.
Nintendo is the king of this, but I also mentioned multiplayer games because they intentionally focus the designer on the mechanics and the levels while leaving the challenge generation to the players (and a whole conversation about how best to matchmake them.)