Well riot has removed a lot of fun things from the game. Back at league's height I saw videos all the time of just plain goofy, fun stuff. Full AP Maokai. The Dunk Squad... or dunkmaster Yi in general. The full revive boogaloo. Funny tribunal cases. Xin Zhao being a man, and teams of 5 supports somehow winning the game. I saw off-meta vids every day back then. Now, not so much.
But things now are so stagnant. You can't bring out fun, goofy or niche picks. You can't make inane team comps and have a chance at winning. Heck, you can't even usually get away with off-meta champs for the role you're in. There are a handful of overloaded or overpowered champs that utterly DOMINATE the game. There are a few items that you ALWAYS build. The strategies and playstyles that win are pretty set in stone, and deviation is punished, both with an in-game loss and your teammates rage. Rigidly enforcing the meta has made the game VERY predictable, since there can really only be a few champs who are "best" for the roles. Enforcing certain playstyles does the same thing. People have figured out the most powerful ways to play and that is how EVERY game is played. It's... less fun. The casual players trying to just play what they want and have fun are pretty harshly punished for it, by their allies raging at them and their enemies curb-stomping them for playing anything less than optimal. In normals. Even in ARAM, there are people who have rigged ARAM accounts to only unlock potent ARAM champs. Not sure how common those are, but I wouldn't be shocked if you ran into one every other game or so.
And even the die-hard ranked fiends aren't enjoying the game like they should either. The people who WANT to play the best champs in the game and want to go super hard for wins are frustrated too. Why? Dynamic queue. Solo players, even when playing the "best" champions and strategies just can't influence the game as much as the premade who are all in voice chat. No, riot has narrowed the game's appeal down to only people playing entirely to win who have a premade of friends playing entirely to win as well. Do you not have 2 or 3 friends who play when you do and want to roll ranked and tryhard? The game isn't catering to you. Oh, you can play it... but all the advantages in the game fall to those guys and their friends and if you run into them you're gonna have a bad time. If they're on your team the game feels like it's in their hands with you a tag-along little brother watching them win or lose the game for you. If they're your enemy you're unfairly facing a group MUCH more coordinated than you, while you struggle to get your team to even respond to pings. Either way is frustrating and not fun at all, even for the diehard ranks grinder spamming the most OP meta champs he can. Even HE isn't enjoying the game.
Riot's choices lately have been pretty awful, and are pushing a lot of people away. I'm one of them. Sooner or later people will drop the game for something new... but right now it's a habit they have nothing to replace. The next big thing to come along with any mass appeal is going to see a mass exodus of disillusioned league players breaking that habit for something new and fun. It's only a matter of time.