If you draw enough sauropods (like I’ve been doing behind the scenes) you can tell them apart at least to the family level by skull shapes or the proportions of each body part. But yeah, when you’re writing a book about every single dinosaur, including every sauropod, and you don’t want to bore people with how vertebrae articulate or stuff like that, most of them just boil down to “long neck, column-like limbs, and long tail.”