Most real life conversations don't require very much careful thought or continuity...

True. My overarching point was that "The following things make real-time communication difficult. Writing mitigates these difficulties". I should change this to be, "The following things make deep RTC difficult. Writing mitigates these difficulties."

But good points about writing, maybe for really important conversations, it would actually be preferable for people to have them via writing even when talking in person would seem intuitive and better.

I think that for "important" things, the goal is often to "take your time, think hard, and get the right answer". Writing does seem to usually be better for this, especially for technical things, but I think it depends a lot.