Are Some Foods More Non-Kosher than Others?

OS 240 Can one food be more non-kosher than another? Last week, a friend’s family who eats a lot of pork and beef invited me over for dinner. They spent a great deal of time avoiding all pork products just for me. However, they didn’t realize that I don’t eat shellfish. I didn’t have the heart to tell them, since they were being so kind to me, so I ate the food. My question is, is for example shrimp worse than non-koshered chicken, or is it just all or nothing?