You don't need animals to craft anything but food. The key to crafting anything meaningful in this game is wood products and scrap metal, not animals. How you would claim that you can't craft much without animals is beyond me. The notion doesn't even make sense.
Animals aren't "very rare" at all. If you're running around town, sure they're going to be rare. The moment you step off the road, you should be finding several animals per hour. Like, a dozen animals per hour or something. Animals are even getting a boost in spawn rate here soon, too. Yes, zombies are lootable. Not all of them have loot. There are 2 ways to loot a zombie. One, when you kill them, there's a chance to receive something in your inventory immediately. Two, when they're on the ground, you can hit them with certain items to get things from their corpse.
Most of the time, zombies won't drop anything in either case.
I used a syringe to draw tainted blood from a zombie earlier. I didn't even know you could do that and I don't know what the tainted blood is used for. There's always something more to learn.
Stop passing around FUD.