Mongols made a major contribution to the development of Europe as the dominant region in the World by bringing gunpowder to the battlefield.
However Mongols under Ghengis failed to capitalize on this technology. Not only that, but they failed to develop the technology, and so did the Chinese.
Gunpowder was known to the Chinese for some time, and to Mongols also (several centuries I belive). And yet it was the Europeans who within two centuries would be blasting the gates down in China, and in 1900s would march through the Forbidden City.
Failure to appreciate and innovate technoology which clearly offered advantage to the Mongols would eventually collapse their empire, and that of the Manchus who inherited it, and end Imperial China for ever. It would see the Chinese dignity trashed as the Japanes, once in awe of the Middle Kingdom, invade China and occupy parts of it for over a decade, and Russians, once 'barbarians' would liberate China from the Japanese.
Sometimes perception of a good commander are short-sighted by immediate decisions and events rather then their consequences. Ghengis Khan failed not only to change his tactics, or adopt new technology, but also instilled this attitude in his followers. In a short time Mongols would be fractured, and their territories shrunk by more adventurous newcomers such as the Ottomans.
Lesson, a great commander also leaves a great legacy.