The DC-X was 9.1 tonnes empty and 19 tonnes full- meaning landing thrust was ~half of takeoff thrust. The Falcon 9 was 400 tonnes full and 26 tonnes empty, so takeoff thrust was >20x higher than landing thrust.

That's a huge engineering difference, roughly like the difference between a car and a helicopter. The Falcon 9 was also 4x taller, meaning 16x more force to correct a lean. A little burp would send the rocket right back up in the air.