They don’t HAVE to come off of formula at 12 months if they are not ready. That is why they have toddler formula. My daughter turns one in 2 weeks and is definitely not ready to stop talking a bottle. Go at your own pace.
I was so worried recently that my daughter was not eating enough solids until I came across a thread on FaceBook saying "food before one is just for fun". I did some research into the validity of that, and discovered it's true! Right now she's just getting used to the idea of eating, and learning all about textures and flavors, but her main nutrition is still milk. Helped me worry way less! Especially since she is a chunky thing, clearly not starving haha!
At 12 months they come off formula. So it's more about leading them towards more food less milk to make it easier getting them off it. We really let her have the reins and the routine we've gotten into is formula for wake up breakfast, second breakfast is a food, nap bottle if we need it. Try a food for lunch, follow with bottle to make sure we ate enough/usually nap part 2. Same routine for dinner/bed. Snacks on demand through day.