More midi-chlorians does mean more force strength, but training and discipline plus a deeper understanding of the force will allow someone with a lower mid-chlorians count to use the force more effectively. It's like having gear. If you have the best gear, you're better prepared to do something. But if you don't know what you're doing, then no matter what gear you have, you won't be able to perform well. Someone who's practiced enough and mastered an art can do incredible things without good gear. But if they HAD that gear, it would help. Anakin was born with the highest midi-chlorians count (The best gear), AND was the Chosen One (He could even replace the Father himself), but without discipline, control, and understanding, he wasn't capable of feats like the ones performed by better force users.