Unless you're high elo, ignore meta and find what works for you
I get frequently QQd at for picking Sivir who is regarded as weak but in pre-season and so far in S8 my winrate is hovering around 80%.
Meanwhile my Ezreal winrate in pre-season and S8 is somewhere around 40%.
and 
main, yeah, you will have games where you completely stomp, sure. I recently played a game on my alt where I went soraka mid with phase rush and deliberately the worst possible runes, and we won. i actually beat Swain mid, i shit you not; I only won by one kill, but still, I beat him, I won my mid lane.