This is the knock-down question for mainstream modern atheist-materialist people, especially when it comes to Christianity. And, so far as I can tell, it is the basis of a solid argument against the Christian conception of God.
If God is indeed omnipotent - as many mainstream Christians insist (at least when they are doing theology); then God could-have made us and the world any way he wanted them to be. At a stroke. Immediately. No route nor rigmarole: just straight-off ideal.
But God didn't do this, we are not ideal and neither is the world - instead God made things very flawed (as Men are and as this world is) - with the idea that at some future point people and the world should end-up the way God wants it to be.
For an omnipotent God to take this indirect and uncertain route to how-God-wants-things-to-be seems absurd, uncertain - and extremely unconvincing. Why on earth would an omnipotent God choose to proceed in such a contingent fashion, when he could simply make everything correctly, first-time?
Of course, the problem is to do with the imputed attribute of omnipotence: the claim that God can do anything that it is possible to do.
The idea of an omnipotent God is not natural to humans, nor is it spontaneous for humans to presumae that their god/s are omnipotent; omnipotence is an abstract philosophical concept; it is not found in any clear, explicitly or unambiguous form in the Bible...
Presumably omnipotence was something which must have been introduced to Christianity (from various schools of Greek and Roman philosophy) after the period covered in the New Testament; and somehow this alien and hostile doctrine has worked its way into the very core of most Christian churches, at the level of mandatory, core dogmatic assertion.
So, most Christian churches and denominations regard the omnipotence of God as an intrinsic part of Christianity - and are forced into elaborate (and unconvincing) ways of trying to avoid the plain paradox of omnipotence.
Because if God is omnipotent, then there is no point or purpose to this flawed world or our mortal lives. Ordinary people see or sense this - and regard the theological explanations as evasions - and they are right to do so: they are evasions.
The reality is that God is working-towards Heaven, because that is the only route by which Heaven can be reached. And God calls upon us to work with him. Heaven is the future consequence of a loving alliance of God the creator and Men who inhabit his creation.
Men cannot be created as they could and should be - as full children of God; Men can only become children of God by experiencing and learning; by their own choices and by God's help. It is, as I said, an alliance - both sides (God and each Man) are needed.
This world could not be created as the full intended state of Heaven; it was instead created as a place of learning and experience by which a Heavenly situation may be achieved; by mutual consent, by mutual love.
In the end we are pushed to a stark choice. Are things the way they are in mortal life and on earth because it is what an omnipotent God wanted? Or is this the best method/ process/ path by which God needs to proceed to get where he wants to be; to achieve his ultimate goals?
Since the Christian God is known to be Good, Christians are (I feel) pretty much required to believe the latter: i.e. that things are as they are, because this is the necessary way to get where we want to go.
We are the world are flawed because because God could-Not make people and the world the way he wants them to be.
And if we want a Heavenly state, we need to join-with God in this work of making.
Heaven is not just a destination, it is a joint-achievement: we are each called-upon to be Heaven's co-creators.