We learned to think by writing only after writing became cheap. Yes, we’ve trained our brains to develop ideas by editing raw thoughts on paper, but it is just one of the possible methods.
I have read a lot of late 18th, 19th and early 20th century books and diaries, and it is plainly clear that writers such as Tolstói, Zweig, Goethe and others developed full books in their mind first, then wrote them from cover to cover in 20-30 days.
Thinking used to be detached from writing. That is a fact. We just lost that ability in the modern era thanks to cheap writing technology: pen and paper, then computers. I'm not saying the current approach is wrong, but don't assume that the only way to think is to write.
Socrates argued that writing would destroy people's memory. He wasn't 100% wrong, yet here we are. The criticism towards the use of LLMs is so deliciously ironic. The analogy with writing... writes itself. Kids that grow up with LLMs will just think differently.