People who are trying to pass it all off as "The Boards are a tiny vocal minority," are ignoring the bigger picture.
Reddit usually a bastion of Pro Play worship and Riot boot licking is popping out threads like; "Discussion: How many people have actually quit League or severely reduced their play time in the past couple of months" Comments about how shit this season is are getting upvoted instead of downvoted.
LCS viewership is down, sometimes by 60%.
Youtube is full of negative video's about league.
Pro players on twitter are increasingly neutral/negative towards Riot.
Fortnite is the darling of Twitch now. Big League Streamers have either quit or keep playing through sheer inertia.
There are tons of anecdotes about "my entire friend group quit league," (I myself am the last of 6 people that used to play together all the time.)
Bitching and negativity in game is high at all elo's.
Burn out is definitely a factor. League is a pretty old game at this point. However the current state of balance, snowballing, damage creep, et cetera is fueling that burn out. Riot has made massive changes to the game this season none of which have actually made the game better or addressed frequently brought up issues.
Ghostcrawler once wrote on his blog, "Another way this is visualized as you being on one mountain peak, and wanting to be at an even higher peak, but having to go down the mountain into a scary valley of chaos before you can climb up to that other peak." Bascially advocating Short Term Pain for Long Term Gain.
Sadly it has been long term pain for no gain.