^^ This!No, Itachi had to train to control his powers, if you get a powerup, doesn't automatically mean you're powerful, you have to get control of that power, just like Naruto training to control the Chakra mode's power.
Remember when Orochimaru was watching Itachi train? What was he training in? Kunai and Shuriken. He also trained his fire techniques.
Also, like the quote above, all the uchiha has sharingans, but that didn't make them automatically powerful. They might have it, but could they use it (effectively)?