Why Did you Pick....

Because some people like Fiora. In order to truly master a champion you have to know how to successfully play them when they are at their strongest and when they are at their weakest. This means picking said champion into bad matchups.

I treat Garen this way, and have ever since I started actually learning how League works back in late season 2. You'll get yelled at for picking your champ into a weak matchup, and sometimes you will make a mistake and things will snowball against you, but being able to stick through it and defy the people who would rather copy than learn is well worth the level of skill you end up with afterward.

I picked Fiora botlane with Leona and dominated (vs Vayne and Zilean). She is good only vs squishies. Vayne did ragequit in the end, she was only feeding whole game.