League of Legends is lacking...
I used to play League of Legends seriously through Season 1-3. This is because I was able, as a solo-player, to carry my team to victory. I remember back in Season 3, my Diamond 5 game was me pulling off a clutch ult and penta-kill with Kayle during a 55 minute game, my team was dead, I ended the game by myself.
Then they changed the game to be more and more team-oriented, not just being able to back on one players skill.
This made the game more frustrating to play, because if a lane lost, the game was one-sided from the start, and if the players didn't know how to come-back then it was a loss.
When I look back at how I could've helped my team do better, everything that was in-game, couldn't help, and still today, when I look at those situations that I had, there's still nothing I can do to help my team while keeping focus on what I'm doing.
With the addition of Voice-chat to Heroes of the Storm just announced today, I'm hoping that League of Legends, and Riot Games will realize how much voice chat is needed for those solo players and how much it will improve their game.
In defense of "Voice-Chat will increase Toxicity". There's a mute function in every game, and after playing Overwatch for the last year, I've not had any problems rising from Plat to Masters just through communication. Imagine if we had these low silver players in League, shot calling and becoming the next Hai... it's something I will continue to wait patiently for while I play other games with in-game voice chat.
TL;DR - Voice Chat would make the game better, allow people who can shot-call to rise in the ranks, and make this Team-Oriented game better for us solo-players.