The new player experience
What happens when a new player asks people what they're in for? They get this:
You will not enjoy it. It has the worst new player experience I have ever had the misfortune of experiencing. It's so fucking bad, I'm level 22 right now and constantly getting matched against level 30's with full runes/keystones while half my team doesn't even have keystones or t3 runes, just what the fuck.
Leveling 20-30 also takes a fucking decade, it's like 300 games or something stupid for those levels and 95% of your games will literally be decided at the loading screen.
Masteries and runes matter too much for riot to think it's ok to match 30's against 20's and 20-25's against 10-15's. I just don't even know what the fuck they're thinking.
It's obvious the majority of the player base is 30 and the new player experience isn't even considered by riot because this games retention rate on new players is probably less than 5% with how awful it is now, and only veterans are left playing so why the fuck would they waste time and resources on something pointless.
TLDR: Shit new game experience, you will playing insufferable 1 sided matches for ~500 matches then still not even have enough champions or runes to fill roles properly unless you spend money on a bunch of champions(like $60-100 worth when they're on sale only).
The XP grind is terrible, the initial champ grind is terrible, the rune grind is inexcusably bad.