I agree. In general, I find the task of "introduce yourself to a specific person" or "make a specific case for something" much much easier than "talk to people about nothing in particular", if only because there is always a specific goal that I keep in mind while talking. So long as I deliver a presentation well and impart all the main ideas, it's going well. I find that small talk is impossible to handle like that because it's too random and there is no specific easy-to-see criterion of success or failure. Others simply paying attention could indeed mean politeness rather than interest.

Staying quiet, I feel, has the unfortunate side effect of making me seem asocial, and I am not quite sure that it is a viable thing to do in a social situation.