That confusion is one reason non-Christians believe that the Bible constantly contradicts itself. Look at it in the context of human evolution. The Old Testament records God as those things because that is what humanity needed at the time. Humans were even primitive in their emotional development, so they needed a god that sent a loud message.
I think what fundamentally religious types don't understand is that the arrival, life, teachings, and death of Jesus Christ were a sign of humanity's evolution and the need for a different god (or God). One that was more interpersonal.
Today, most Post-Protestant churches view God as "just" rather than "vengeful". In answer to your comment on "mediocrity", I would say that the current awareness of the interpersonal nature of God helps people understand that it wasn't perfection He was after, but a creation that he could interact with and that would appreciate Him as Creator (ie, worship).
Attending Mars Hill Church in Seattle.