Games aren't decided by the "15 minute mark"
Umm, sure they aren't.
This one def wasn't over by the 8 minute mark, and it def doesn't just take 10 minutes to slowly finish their entire base.
https://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2723576640/33518097?tab=overview
This is what players are complaining about. The games may take 20-30 minutes, but the last 10 minutes (which in a 20 minute game is half the game) is just slowly destroying their entire base.
There is a 75% chance of winning if you get first blood (typically minutes 1-5), first dragon, (minute 5-7) First tower (minute 10) That means you have a 25% chance of winning against those conditions which happen in the first 10 minutes. https://www.leagueofgraphs.com/infographics/patch-8-3-infographics
IT just doesn't make for a healthy game when you play 10 minutes of a game just to end. It makes it where you literally are just slowly dying for the rest of the game. No wonder we have such mental issues with this game.