People doing presentations almost invariably have a façade on and what they're saying is either carefully vetted to avoid giving offense and/or is done with the purpose of projecting a very specific impression and/or generating a very specific response.
When it comes to making up your mind about somebody and their ideas, watching a presentation at a conference it's just slightly better than watching a politican on TV, which is about the most staged, carefully managed image of a person you can get.
IMHO, even as difficult as it is for introverts, the best way to discover good people with open minds and interesting ideas is when casually chatting with other equally anonymous attendees and that's not something possible via video-conference.