How to get a team comp?

Does anyone have tips for getting people to work together and not auto lock yi,zed,quinn,graves,etc. The amount of games I see lost because of extremely selfish carry picks that end up getting steam rolled in fights because the enemy had a comp is unreal. For a specific example, yesterday we had a fed graves, zed AND rengar. Three fed hard carries. What happened? The 2 tanks and off-tank on the other team cc locked them into oblivion while their assassin dived our adc/supp for free because no front line / tank is op.

How is it fun for people to auto-lock selfish champs and then lose the game solely because of it...