Morning Scepticism: Philosophy Of Religion

When I hear arguments around the existence of God, I really think I must be missing something elementary. Take JL Mackie's Evil and Omnipotence, a paper that details the incompatibilities with the notion of an all-powerful deity and the evidential existence of evil. When I read something like that, I just can't get passed the notion of ascribing omnipotence to begin with. That it's incompatible with a world containing evil is the least of the worries. Yet there are plenty of philosophers who take these kinds of arguments seriously, so I'm fairly sure the problem is on my end. What am I missing?