You shouldn't have to teach your social circle how to be a good friends.
You're planning on throwing a party. You send invites out to your social circle. Some take days to reply, some respond immediately. My biggest issue is when they reply with something unrelated to the invitation or give you a "maybe" answer. I shouldn't have to remind full grown adults to RSVP to something they've been invited to. It is frustrating, rude and inconsiderate. We're talking about a party where as the host I am responsible for spending money on food, drinks and taking care of entertainment being available. People in their late 20's should already know that. A yes or no answer is all I need from you. And then there's the "maybe" which is probably even worse because it implies you're waiting for something better than my party to come up so you could attend that instead.