Because they make tradeoffs in other directions. Its not always a linear thing.
Kat - A melee assassin stuck in a ranged lane. And her full combo requires a channel, so its worse if her opponent has any hard cc.
Riven - Second lowest base regen in the game, with Mini Gnar taking first. Relies on her rapid engages and disengages and suffers against bruisers that can keep up with her. Guess which lane she's taken in?
Yasuo - Has to rely on his windwall and flow to survive lane. Too squishy for top, too weak for the jungle.
Garen - Its.. Garen. He'll never be great, but never that terrible either. Kind of the poster child for a guy always in the middle.