The saying that "great talkers are little does" is a charge that someone is talking big but not accomplishing anything.
The saying goes for those who speak in great length about what they would do about various topics. They spend time by just saying and describing about the plans they would launch. But to execute is a different issue. These kind of people just love to gather some listeners but they are not interested in actually doing that. Actual doers will not waste time to preach, they would practice because they need the satisfaction of only the work done. The famous saying ' Do not preach but practice' establishes this fact.