Isn't LoL dead yet?

Nope it is not, (or not yet at least)
RIOT the company behind it is trying so hard to keep it alive by making changes evecry patch (usually ever 2 weeks) , releasing new chamions every 2-3 months (Ther is 140 of them now) , and reworking (both graphicly and gameplay wise) old champs that do not fit into the new design concepts of the game.
In addition to that they are orgnazing yearly 2 worldwide championship (Worlds and MSI) that are big e-sports events costing millions of dollars to put up and do attract a lot of new players to the community.
So i think LoL is pretty 'healthy' as a game for 6 or so more years.