The actual level of variation in Civ5 is less than people think. There are currently 3 factors that civs differ in: UU(s), UA, and if lucky, maybe a UB or UI. But in reality, usually this is less. Most games, the UU never really even enters the game, and it almost never has the power to change anything. Take Byzantium for instance. They have 2 next to pointless UUs that will almost never impact the game, and in reality the only way they differ from other civs is that they might get an extra religion belief.
In BtS, you had civs with different starting techs to consider, different UUs and everyone got a UB, plus two leader traits on top of that. All together, that's 4 or 5 spots of variation depending on how you count, compared to 1 or 2 in BNW.