I agree that it can be daunting. I knew nobody and nothing when I went to my first convention, the 1984 Worldcon. The Big-is-Everything crowd can scoff, but 8000 people was huge in 1984. I was fortunate in a sense because my "anchor" was to deliver a sketch that a friend of mine had drawn for the Pinis (of Elfquest; the reason I even went was for the "End of the Quest Party" they were holding there to celebrate the release of the final issue of the original series). Even more helpful was that the person in line behind me to pay for a membership was a friend of that friend. So before I'd even bought my membership, I had made an acquaintance and that helped.

OTOH, something that doesn't help is if a clot of, say, ten people go to a Monster Huge Convention and never talk to anyone else and just huddle together gawping at everything around them.

The kinds of conventions I enjoy are not in general a place for what might be called "tourists." I expect everyone to be part of the act. That's why I use the Fandom as a Pot-Luck Dinner metaphor. That model doesn't work well for 100,000-person pop culture fests, but I think it's still plausible for Worldcons up to the approximately 10,000-person size, at which point the convention would be a lot less expensive per person to organize because I don't think we'd outgrow our current size of convention facilities.