I guess I'd have to consider myself a reasonably picky eater, but not one of those people who's always trying to make substitutions. If it's a home-cooked meal, I'll try almost anything, and I've yet to visit a restaurant where there's not at least something that sounds good. But I'm not usually in favor of the whole "let's all order something and share" dining... it's inevitable that someone will want something that I don't care for - be it rare/greasy meat, something slimy (jellyfish, raw fish, etc.), or that most repugnant of pseudo-foods, ketchup.
When I was a kid, my Dad told us about a friend of his when he was growing up whose parents gave them an ultimatum upon turning 13... basically, it went as follows: "You're a teenager -- order what you want, but no substitutions." In general, I think that's a pretty good rule -- with the exception that a lot more places these days have more options, rather than "the standard".