To be frank, each year, every game would die due to the increasing number of games available to play, especially games of the same genre, which could mean competition. I had once declared League as dead due to the major imbalance of bot lane (patch 8.12 a.k.a bot lane fiesta) which I did not like at all. As a result, I moved to Fortnite due to its exploding popularity. But after a few months playing Fortnite, I felt worn out by the game and decided to move back. League felt good again. And not to mention, Worlds 2018 + KDA skins.
Overall, each game has their ups and downs. League is such an old game you could hear players saying its a dying or dead game.