Just because someone can use the force doesn't mean they could have overthrown the Empire, defeated Vader, redeemed Anakin, killed the emperor, etc etc. What strength did Luke need to defeat the Empire? Was it his quick reflexes, his skill with a lightsaber, how many rocks he could lift? No, clearly these things helped but they were not sufficient in themselves. Luke is his family, and so is Leia. That is why Leia is the other hope. Luke also won through his emotional understanding of Anakin, and his mindfulness.

Thinking that other force users living makes Luke or Leia trivial misses entirely what makes them special. The other Jedi have their own paths to walk, and it is not necessarily their responsibility to overthrow the Empire. There other ways to serve life and more generally the force.