League isn't dying because any specific character or game related things, but moreso because the competition around it is slowly getting better. Games similar to league are being released on mobile devices now, which not only target a broader audience (as the games tend to be shorter allowing people to better fit them into their schedule) but with little to no repercussion from the game studio doing so. League is and has always been a "niche" game so to speak, as oftentimes the playerbase has to have a few if not all of the following requirements:
-The ability to stay in the game for 1+ hours (queues included in this time parameter)
-The ability to "handle" tilt
-Decent computer specs/internet
-The ability to understand multiple different real-time concepts (cs'ing, vision, trading)
With the competition out there, you oftentimes at best need to understand like 1-2 of those.