Excuse me, but if you read my post before, I said that lots of people underestimate new players intelligence and willingness to learn, but not me.
And with most of new players that was my experience, with few only not wanting to put time into learning the game and being there just "for the lulz" and because their friends are playing it.
my good friend was that in one campaign, he is very intelligent guy, but he simply didn't put much effort in playing the game or learning it.
From 3rd to 6th level(9 or 10 sessions) he was "just there".
Lowest common denominator are people not willing to learn the game for real. Met few of them, luckily in minority.
All the new players that like the game will learn it. Yes, first session or two they will suck at it, but that is the process of learning, you need to suck at something first before you can be good at it.
Give them option to swap spells/feats/skills/subclasses after every session if needed, it's even better way to learn.
Even if they want to make completely new character after two sessions, it's ok to let them.