I would argue Cait is above average at all points of the game. Early game her naturally high range gives her good lane presence, mid game she has good skill damage and clean up, and late game she has decent mobility and jukes with her e and w and her range keeps her out of danger, making her hard to take out of the fight. And if worse comes to worse, you can just retreat and then ult a target from safety for some nifty burst.
Also, you can cast E and Q at virtually the same time, allowing for some nifty combos. For example, Q at the enemy, and hit E during the cast time at the enemy for both skills to hit for more damage. Or the pussy way of E first followed by Q to hit the slowed target. Or, my favorite version, the E away from the target to push yourself towards them, then Q during the push to catch the person off guard from the slight boost in range, and maybe result in enough damage for your ult to finish them off. If done right, the channel time for your Q should take the same amount of time as your E pushes you, so you don't have to stay in one place to channel your Q. Heck, your ult and w both work while using E as well, so you can be sliding all over the place while using your skills.
So while she's not stellar in any one area, I would argue she's good because she's consistent and versatile. She's one of my favorite AD carries alongside Kog and MF. She also has some bangin' skins. I have Resistance, Sheriff, and Arctic Warfare :3