The topic of animal sacrifice is one that a lot of modern pagans tend to avoid, to the extent that at least one of the pagan message boards I've been a member of over the years has actually banned the topic. Even a hypothetical or historical discussion is against the rules.
I think part of this is a misunderstanding of what animal sacrifice entails. Common objections are that it's cruel to the animal, or a waste of food. Now to be fair, there have been many different cultures which practiced animal sacrifice, and they didn't all do it in the same way. Many cultures, however, brought the animal to the altar where it would be quickly killed, and then a part of the animal would be offered to a deity, or deities, and the rest would be shared among those present in a communal meal. In some cases, the part offered to the deities wouldn't even be a great part of the meat - in ancient Greece the more inedible parts of the animal were commonly the offering.
When I was younger one of my uncles raised pigs, and the whole family looked forward to the pig roast. He raised these animals with care, he knew what they ate, how they lived, and when the time came they were killed quickly. Family came from all around for this giant meal. I didn't even eat meat at the time, this was during my vegetarian years, but I still enjoyed getting to see all of my cousins, my extended family, getting to run around the fields, and of course who doesn't like side dishes? Now, no part of the pig was given as any sort of offering, but to me, that's really part of the spirit of an animal sacrifice. It's a family meal, where the Gods are honored as part of the family, as honored guests that we appreciate. The animals were killed anyway for the meat, does it really change much of part of the animal is given to the Gods?
Of course, most of us don't raise our own animals, myself included. (Although perhaps we fish, or even hunt? But that is a topic for another time.) While we can still certainly make offerings and have family meals, we no longer have that context where it would make sense to preform animal sacrifice. Still, when we do look at it in context, is it really that strange? Unless we're a vegetarian or vegan, we eat meat, and to eat that meat someone raised and killed that animal - and if someone chooses to raise their own meat, and they want to offer some of it... well, I just don't see why that's such a big deal. This shouldn't be the forbidden topic that it's often made out to be.