I don't know what you mean by talking about God abiding by today's standards or past standards.
Are they God's standards or human standards?
Who is deciding the moral standards of the day - God or humans?
Surely an eternal being should have eternal standards. Or at least they ought to have been developed beyond those of bronze age humans long before God was smart enough to create the universe.
You ask "What purpose does it serve to judge God's past actions by today's standards". Well, my purpose is to show what a lot of nonsense the Bible is as a moral code and how unlikely it is that anything like the God of the Bible ever existed.
And I would ask, bearing in mind that "purpose" of life is a major facet to the Christian doctrine, what purpose does it serve for God to demand certain moral behaviour, and wipe out civilisations that fail to abide by that standard, and then change the standard over time? What IS God's purpose? And why should we pay any attention to him?