This is gonna be a long ass post, so if you don't want to read it, then skip this post. But I'm going to be going very in-depth about the statistics of this game and if it really is dying.
First and foremost, if you look at the link at the top of this post, you'll see the search popularity of the term "league of legends" on google in the past 14ish years. So of course, it was zero before the game was actually released, and then had a pretty steady incline until about 2013, when it went down, then back up in 2014, and now it has been in decline since then. This doesn't automatically mean the game is dying, but it is an indicator nonetheless.
This isn't a real statistic, but either way:
There are a lot of random trends of people searching this throughout the years, but it really started to skyrocket over the past couple of months (the highest it's ever been). This doesn't really mean much, but it shows that people are aware.
This isn't a statistic, but it's worth noting.
Many league of legends content creators have stopped playing the game, or stopped producing league of legends related content. And this doesn't show that the game is dying, but many of their fans have also stopped playing the game because these streamers have given reasons why they don't like the game anymore, and many people aren't finding it fun to play anymore. These people include: videogamedunkey, keyori, nightblue3 (i think. he said he quit and he hasn't uploaded a video in a week, but then again, many people said they would quit and never did). You can probably find more, but dunkey was the main one that caused an "uproar" if you will. Also, many people that don't play the game or that have quit the game think it's very toxic and has a generally toxic community.
I think the game is way too competitive, which is why the player base is not going up. It's also changing so fast that, if you take a month break or a couple month break from this game, it's basically a different game when you come back. And while it is good to keep games fresh and updated, many of these "updates" are based around esports, which is a large investment for Riot. As well, when I got banned and made a smurf account, I rarely saw any new players in my games. And when there were new players, they did terrible because of all the smurfs that were tryharding to level up their account. So this game doesn't really cater to new players all that much. BUT: Riot did gain some more players with the unbanning of Tyler1, so I guess that's something. But many people just don't like the game anymore, and I can see why. It's become way more competitive than it was in say, season 4. People aren't quitting because they're bored of the game, people are quitting because it pisses them off, or because it's too competitive for them and they want a more "fun" game, for lack of a better word. I personally don't think this game is as fun as it was when I started, but many people still find the game fun, so I think League isn't going to die any time soon. I think it is dying very slowly, but not fast enough to consider it a "dying" game.
P.S.: I think the main reason this game is actually dying is because tyler1 banned me from his stream for saying "duo with voyboy". kappa