I like the idea of inviting with the specific purpose mentioned (it's gumbo night!) and letting people decided.
To clarify - this isn't my normal mode of inviting. My normal appropach would be to have people over in the evening and serve a variety of appetizers, partially because doing a full meal is so complicated, or something casual where we boil pasta and dump sauce on it. If I have a dinner party focussed around a group of people (say my Chinese class), I cook something that everyone can eat.
Occasionally, however, I like to cook a complicated, multi part meal to share - I like to cook and I'm good at it. Doing this for a random assortment of people from my social people typically involves factoring in the vegetarians, non drinkers, people who dislike spicy food, people who are allergic to nuts and shellfish, lactose intolerant and gluten intolerant people and so on.
I'm also one of the only ones of my group of friends who actually has a kitchen, and my kitchen consists of two burners, a microwave, a toaster oven and a rice cooker, and a fridge shared with six other people, which makes preparing multiple dishes or co-hosting awkward - preparing one meal takes some planning and modification of the usual cooking techniques. Most people have a hot plate and a kettle, and that's it.
I think my fundamental issue is always having to cook to the lowest common denominator. I don't like inviting someone knowing that they can't eat what I'm preparing, but in order to produce something that everyone can eat, I either have to cook from a fairly limited selection of dishes, or cook multiple meals. And there are some dishes which are really not meant to be cooked for one person.
