The other thing I wondered about is what you said about motivation, that everybody likes to learn, so motivation is not difficult. That certainly holds true for many members of my family but not for everybody.
My youngest has shown a very strong disinclination for anything requiring effort or pushing himself (except recently as regards physical exercise). Despite a home environment full of story-telling and music and outdoor trips, he never really wanted to make an effort to learn anything. He also wasn't interested in crafts or doing anything with his hands, he wasn't interested in playing an instrument or learning DIY or learning to cook.
He did learn how to read eventually because school (and his parents!) insisted, but he has never read a book voluntarily or for pleasure. It wasn't just about being unhappy at school: he was the same before he started school and he was the same during his very free, outdoorsy summer holidays. We lived near the sea and though he eventually learned to swim well, he never pushed himself to learn more difficult things or learn more quickly like the other children did. If it was combined with any effort or risk of not getting it immediately, he didn't want to know. He simply is the least driven person I have ever come across.
He is now holding down an unskilled job and doing his duty in it, because he knows he has to. The only other environment he did well in was the Uniformed Services BTEC which he did instead of A-levels. He was fine with being told to do push-ups, the only problem there was that he really didn't want to join the army.
He is a pleasant and helpful young man, but he seems to feel no need to conquer new worlds or explore new territory. It's not a mindset I can understand, but there clearly are people like that, and I wonder if it is even possible to home-school someone with that personality.