Four hundred years was a long time for the Israelites to live in slavery. Entire generations never tasted political or personal freedom. This seems very harsh from God since we tend to elevate personal freedom to the greatest good. But God often has a very different plan.
While we cling to our quality of life, God clings to His people. Suffering, slavery, or poor life quality cannot hinder an intimate relationship with God. Does it mean that freedom from oppression is not important to God here and now? No, but it is not paramount because in knowing Him, we are truly free!
At the same time, God is not unmoved by suffering. He spared Moses and planned to send him to free his people from Egypt. Moses was only foreshadowing the great Exodus that Jesus would accomplish by freeing His people from the bondage of sin and death. We still live as refugees, pilgrims on our way to the eternal Promised Land. When Jesus comes back, injustice, oppression, and satanic tyranny will be eradicated. We will live in peace and freedom forever!