"Burden of Knowledge"
The Burden of Knowledge for LoL is ridiculous. 100+ champions some of whom are played in <10% of games makes for a ridiculous learning curve.
I don't know how new players handle it.
You have to know: (1) champion abilities (400+), (2) their hitboxes (which don't always correspond to the visual), (3) their scaling (which differs based upon how fed etc..), (4) trading, (5) get a sense for how much buffs/pots change trades and teamfights, (6) different builds for different champions...
I used to play RTS games and you didn't have to know 1/10th as much to play at a mid tier level.