How is twisted fate good

I dont really understand why people say that twisted fate is a good champion to carry with. Iv been playing with him for a while but he just dosent do as much damage compared to other champions like akali and i dont think he can compete with them. Just the other day I tried to use my ulti on a galio when he was extremely low but then he cc me and then I got one shot. in teamfights all I can really do against heavy dmg champions is stay at the back, use my gold card and q. That barely does half my opponents health even if they are squishies and I have to leave it up to the rest of my team. If I get caught with morgana q or lux q for example, its pretty much over. I used to main Akali and I had no trouble winning lane and one shot-ing ad carries. In team fights this would be really good because then I would hide in shroud and get the tanks and whoever is left after cool down. Even if tf has the ability to roam and pick off kills, he isnt really that good if he dosent have the kill potential like others to back it up, espicially when the enemy outscales and groups late game. Considering tf's low dmg compared to others, and his weakness in terms of being squishy, can someone pls explain to me the reason why he is called on of the best carries for mid lane.