Frankly, playing an RPG isn't a conversation. I don't pretend to be someone else during a conversation (generally), nor am I trying to convey that new person to everyone else around me during a conversation.
So, yeah, I'd say that's where the greater disconnect lies. Playing an RPG and particularly role playing during an RPG, while still of course using language, is not a conversation. A conversation is the back and forth introduction and examination of ideas with the purpose of communicating some sort of information.
Role playing, otoh, is attempting to portray some sort of character to the people at the table in such a way that the other people can get some sort of mental image of what you are. There's very little back and forth. It's primarily a performance. And that performance is judged by the people at the table. A player who is nothing but a dice bot with a heart beat is communicating excellently - he's playing the game. But, he's not someone I want at my table.
While you CAN convey emotion during a conversation, the point of a conversation is rarely to evoke emotion in the other person. ((Although, I've certainly had conversations that have evoked quite strong emotions)) In fact, typically, evoking a strong emotion from the other person isn't what you wanted to do, but, because of something someone said, a strong emotion comes out.
OTOH, in a performance, the entire point is to evoke emotions in other people.