3v3 wasnt very popular because its basically a miniature version of summoners rift, you still have 2 solo lanes and a jungler, it was irrelevant but a 2v2 single lane map could be very interesting for people who like to duo
With my experience in Twisted Treeline, the successful teams had a duo lane instead of a jungler. The cool thing about that gamemode is that you had way more impact than in 5v5 because you were a whole third of the team.
But people like monotony, I guess...
I'm fully in favor of bringing back 1v1 and 2v2 as both normal ranked modes.
3V3 wasn't popular because riot let it get overrun with bots and then stopped updating it. If they showed it any love, people would play. Same with Domination. both were incredibly fun, but this game is now a Esport game so having simple fun can't haapen.
