Text is one way. You cannot have a fluid conversation via text. Voice and voice+video are faster, plus they carry more information, prevent misunderstandings etc.
Instant messaging is synchronous two-way communication like voice and video. I'm not sure what you mean by "fluid" conversation, though. Voice is good for people who aren't good at typing or expressing themselves via text. However, I don't see what additional conversationally-useful information is conveyed by video of people's faces.
Maybe I just spend too much time listening to the radio and podcasts? Maybe it was growing up in an era where voice phone conversations were more common than texting and facetime?
Yes, good luck explaining things to people who can't understand basic instructions via text. You might use it for "records" to protect yourself, but getting things done is easier. When I ask someone 'do you understand', in text it might sound very aggressive and sometimes offensive. Via phone or video, it is much more relaxed. If you are concerned about recording, just use screen capture and save it somewhere for a while. Even text cannot be used as a clear evidence, the other person simply says 'I didn't understand that sentence that way'.
Maybe I just spend too much time listening to the radio and podcasts? Maybe it was growing up in an era where voice phone conversations were more common than texting and facetime?