I don't get it

So I played a ranked game today, first in a while. I'm probably considered a noob since its only my 5th ranked game this season. Yet each game there is always someone who trolls. Just this last game I got to first pick and went for top. The last teammate to pick chooses a champ for our jungler role. I see this person takes flash/smite. Yet at the last second this person, for whatever reason, decides to switch their summoner's to flash/ignite. So in game everyone tells me to jungle even though I don't know how to and don't have smite. I play ranked very rarely but each time it's a bad experience. I don't get it. I reported this person at the end of the game (we lost, surprise surprise). So if something happens to this person the damage is already done. My overall score is affected by this one troll. Why hasn't riot done anything about this yet? Riot claims to have started a more severe penalty but it seems they still support this type of behavior since they allow a troll to affect my score. How do u climb to a better standing if trolls are allowed to affect everyone's score in this way? How is this a team game if riot indirectly supports trolls?