Because at one point, the game held a higher standard for game play, content, and ranked system design.
Understandably yes, no matter what its free and they don't have to care what we think since people pay thousands of dollars for skins and they basically keep it free (Thank you). But that's not to say the player base cant hold them accountable.
Additionally, the primary problems in the game right now are their own doing. So you may defend Riot but to say its wrong to be upset with them in the current game state is silly (in nice words). Additionally, they have only gotten bigger, only gotten money, and don't have any excuse to not be on top of a game they've now run for 10 YEARS and also do yearly international events with "21.8 million Average Minute Audience (AMA)"(worlds 2019).
If thats not enough, on a more humorous note, remember they claim they are a small indi-game company... but with 200+ years of experience in game design. So it seems like they've burned their excuses. Which means its blatant disregard for its players which is frustrating since LOL has no considerable competitors, that I see atleast.