I should have been more clear — when I say fundamental skill, I mean fundamental physical skill. Maybe ‘activity’ would have been a better word choice. I completely agree that thinking clearly is what’s most important.
I stand by the assertion that touch typing improves writing quality though. It’s hard to articulate your thoughts clearly in text if the act of typing them is laborious for you, the same way it’s hard for someone with a speech impediment to make themselves heard.