Yes, in many cases, a sticky derailleur can be fixed without replacement. Start by cleaning the derailleur thoroughly using a degreaser and a brush. Once cleaned, apply a lubricant to the moving parts of the derailleur. Move the derailleur back and forth to distribute the lubricant. If the issue persists, you may need to take the derailleur apart for a more thorough cleaning or consider replacing it if it's severely worn.