I homeschooled. My sons had trouble learning to write and one really hated writing.
I spent several years having him verbally explain material to me, having him learn grammar and vocabulary and other essentials from entertaining videos and graphic books and such.
Thinking and writing don't have to be so closely intertwined as they are in Paul Graham's mind. He's a writer and writing helps him think.
Some people think while taking long walks, working out at the gym, drawing their ideas, etc.
The kind of thinking Paul Graham does may become less common. I have no reason to believe that's some kind of holy grail and thinking via other means is inherently less valuable.
I say this as a blogger who may be even more guilty than Paul Graham of using writing to help me think.