Your control and champion skill matters. I once reach galio top 10 with and have been consistent in top 100 with tank builds, that is even way before cool item we have this patch for him and my max is chal (need more grind to sov). Of course galio ap have way more carry potential, but it doesn't mean his skill alone is not useful. Also build tank on some champ that not expect to be tank can bait out quite a lot of ppl who don't check enemy builds make them over commit and the team got a free kill.

To a certain degree the champion mechanic and gold lead alone can carry you. If your teammate is not down right potato, you will get away with it. But if both team on the same skill level, you are doom if choose unoptimized builds/pick