Old ductwork, broken, rusted, not sealed. Repair or Replace?

All right, I think y'all can see what's in front of us. This guy's complaining of poor airflow, and we're about to look around. A damper in it. Old furnace, it looks like an old furnace down here. Let's see what we got here. looks like a box for an over and under return on the bottom, supply on the top. Look at that old furnace still down here. Look how old that thing is. Cause this don't work Easily 20, 30, maybe 40 years old. Look at this old thing. That thing might be 50 years old, an Norman Southerner Never heard of that name This, you saw his duct work has some problems. I'm not sure I would have gone the way they did.