Everyone has had games where a teamate does absolutely nothing, just walks around to avoid the AFK penalty, maybe farms a sidelane and "gets caught out". They don't usually type at all either. Riot's ban system is so flawed at catching these people who run rampant. I recently lost my gold 5 promos because of 2 soft inters in a row. No matter how much 4 people want to win 1 person can ruin that and not get punished because they didn't type the no-no words.
I'm not trying to say I have a solution to this issue, it seems hard to detect. But it really needs to be dealt with.