If God didn’t like the way the world was, couldn’t he just destroy it and make a new one?

Yes.  God could have done that and it seems like the logical thing to do.  But we have to remember that what is logical to us is limited by our small minds.

But God is the God of Second Chances.  That is what forgiveness is all about.  That is where hope and faith come into play.

God created us and declared that we are indeed good.  But then sin came into the world.  It is important to remember that God did not create sin, sin is the unfortunate consequence of giving us the ability to love.  If we have the ability to love, we also have the ability to not love.

God chose not to destroy the world but to change it.  Just as baptism is a washing in water of sin from the soul, the flood was a washing in water of sin from the world.  And God knows, through his wisdom that is beyond our understanding, that the love of Christ is more transformative than any threat could ever be.