Why Is My Bot Team Always Bad?

Every game I play it is always bot team feeding. I dont worry about mid feeding, top, or jungle, its always bot. I main top lane so I cannot really gank bot unless theyre getting ganked, thats when id tp down there. But then I wont be able to gank for a long time due to TP cooldown, otherwise id lose my lane.

So i decided to go mid the last 4 games as Veigar, the most brain dead mid laner. I camped bot lane so hard every game, getting them first tower, getting them 4 kill, and they still cost us the game! I dont get it. For instance Sivir last game, she would just keep going in the jungle with 3 enemies attack our inhib, then shed die to a teemo camping blue. I end up going 15/2/17 in 35 minutes, most damage by a long shot, but I still lose because Sivir kept feeding even when I give her the gold lead. This happened 3 games ago as well, I ended up going 18/7/13, ganking bot nonstop getting them fed, and they throw! How can I win!?