Whenever I’m in this situation, I always try to learn as much as I can about the topic, if only to contribute to the conversation. You can also break it down and/or take it in a different (but related) direction. Say they’re talking about how much they love their new toy poodle. You may not give a crap, but you could ask about why they chose that particular breed of dog, whether they like dogs or cats better, even what they might think about domestication of animals. It seems like it’s really the specifics that are holding you back. If you get the topic broader, you can have a discussion that benefits the whole group.

You can always ask questions about the topic to learn more about it.