Why do people play shit champions and complain??
Forreal.
I've been playing Singed since S2 to now S7 almost exclusively and have been Diamond and Rank 1 with him for several seasons. I know he's weak but I never complain and just press on. But you see other people playing weak ass champions and always ask for buffs or fixes and it gets mad annoying! Think about it, I played a champion that didn't even do damage to Baron for years because of a bug and Riot openly hates!
As for why I am probably so chill, I played Yu-Gi-Oh competitively for years and still go back and forth. There, you're at the mercy of a company (Konami) that provenly does not give a shit about you or balance and only your money so you get used to these things. I myself play cheap decks and do fine but can't bitch if I don't keep up with the meta powercreep.
Riot is the same thing so get over it! They only care for what's meta and money, you have no right to complain if you play something weak.