Part of the reason we can criticize these pantheons is that we're looking at them from a retroactive context, as well as comparing them to other religions that have also ceased to exist.
If we were living in ancient Greece, men (unfortunately mostly men) would be empowered by the tales of conflict that involved the gods. To them it wasn't insecurity, the emphasis was on the victory of Zeus over the old order, true justice triumphing over the barbarism of the Titans. It was a standard to live by, to aspire to. We men would not see Zeus as being insecure, rather his victories over his adversaries, not to mention his ability to sleep around and mostly get away with it, is demonstrative of his power and strength.
Today, he's certainly an insecure, unfaithful and misogynistic figure, but back then it was an expression of the authority of men. The bickering of the gods, and the conflicts amongst themselves, was seen as a sign of why humanity is vulnerable and should be just and authoritative to prevent these things from happening. Because where the gods are immortal and omnipotent, we are not; we can't resolve our own conflicts as easily. Justice comes from the resolution of conflict in your favour, and if you can exercise that, you are behaving as the gods, and being faithful.
If we expressed resentment towards the gods for this attitude and called them insecure and petty, we'd be tried and/or executed for heresy, and several notable philosophers were. This is a luxury we have today for living in a society which mostly does not tolerate certain commonplace attitudes of the Classical civilizations, like gender inequality and slavery.
Not to mention that the study of mythology is also a study of human attitude, anthropology and sociology besides history and stories. We're inclined to project our own opinions from this.