What does Romans 8:21 mean?

Paul has painted a dark picture. Unfortunately, it is an honest representation of the sin-ravaged world in which we live. All of creation suffers in frustration under the curses of God in response to sin (Genesis 3:14, 17–19). In response to Adam's rebellion in the garden, God subjected His perfect creation to frustration and futility. This brought pain, suffering, meaninglessness, and death.

Paul has been clear that the story is not over, though. Creation is waiting, longing, for God's children to be revealed in glory (Romans 8:19). That's the day when all will begin to be made right (1 John 3:2). Somehow, at some level, the creation knows this and anticipates it. Mysteriously, a key component of what will happen on that day is that God's glory will be revealed to all and revealed in those who have faith in Christ (Romans 3:26).

Now Paul concludes his thought from the previous verse. God didn't subject creation to decay, to frustration, out of pettiness or revenge. Instead, He acted in hope of—here meaning "looking forward to"—the reversal of His curses. He never intended for His creation to experience this futility and death and corruption forever. It won't. The day is coming when God will reveal His children in the glory He has for us, and then creation will be set free from its bondage. Paul says that creation itself will obtain the same freedom that those in Christ will receive when they are glorified. All suffering will end. All will be made right (Revelation 21:1–4).