Usually when I see this kind of thing it's when someone's playing a champ for the first time or when they make a couple mistakes. Then someone on their team starts being negative or toxic towards said player.
Now I'm not condoning intentional feeding, giving up, or anything of the sort. But why be so serious and harsh? There's a difference between straight-up criticism & advice, and taking it too far with your attitude. I mean, what do you expect? That everyone have perfect mechanics and that they be able to make the right decision every time? Cut them some slack, everyone makes mistakes. You can't learn if you don't screw up sometimes. However it's not your job to hate on them for those mistakes, you should be understanding and honest with your advice and criticism.
Even though I don't think ranked is any more of a place for negativity than normals, it is clear that there is much less on the line, and that normals are (typically) less competitive. Just because people play less competitively than you doesn't mean they're "playing to lose." If it annoys you so much that other players are not as competitive as you then you should either stick solely to ranked or work on that attitude of yours. Because people like you are the people that ruin my casual and fun normal games.