The controller of the enchanted creature still decides which player or planeswalker the creature attacks.

If, during its controller’s declare attackers step, the enchanted creature is tapped, is affected by a spell or ability that says it can’t attack, or hasn’t been under that player’s control continuously since the turn began (and doesn’t have haste), then it doesn’t attack. If there’s a cost associated with having a creature attack, the player isn’t forced to pay that cost, so it doesn’t have to attack in that case either.