I don't know the current status of League onboarding but as a veteran I attempted and accompanied various people throught it in the years and it's been painfully, criminally bad for the longest time. Both when there was nothing but the weekly free rotation to pick from and haveing to sink a month of grinding to get a single champ, till the more recent "we gift you a champ every 2 levels so you can actually play the game".

I think it used (still does?) to boil down to the delicate balance of:

1. the attrition of the early grind is the easiest to monetyze

2. the need for new players to keep the game alive

3. the miracolous success of the game making no changes better than changing something and finding out you inadvertedly sapped the magic out of it.