Namaste, Ratikala
I am not sure why the numbers upset people; a majority identify - on some level - as Vaishnav but I think that excludes folk Hinduism which tends to be much more polytheistic and devoted to a male Deva with many female forms of Devi about, particularly Her ferocious forms. A smaller minority are Shaivas and an even smaller minority are Shaktas although, again, excluding folk Hinduism which tends to worship many, many forms of Devi.
And now, back to the topic of animal sacrifice! I do not think it will ever be completely obliterated; animal sacrifice holds a strong place in many, many religions, not just Hinduism. Vaisnavas and Shaivas have moved mostly away from this form of practice (although I believe if we looked hard enough we would find forms of both who accept such sacrifices) while Shaktas still accept it on the whole. People may argue this is because Shaktism is a less evolved form but it could also be argued that, a sacrifice done properly, is good for the people and the animals. For instance, the animal is released into the next - hopefully human - life, the sacrificer (usually wealthy) gains punya for feeding the needy and the priests officiating follow their karma. It is not, necessarily a bad thing...
However, it is a horrible thing when millions of animals are slaughtered with no skill, thereby torturing them needlessly, and their meat goes to waste. Are all of these animals going to be eaten? Really? I doubt it. If each animal's carcass were going to be used, for food, for leather, etc than it is not mindless killing. But if it is just killing to appease Mata ji... I do not think She would approve of that. Mindless slaughter is never any good for anyone.
And of course, let us remember that animal sacrifice tends to occur in regions where other protein sources are scarce, so again there is an evolutionary reason behind it... but food is no longer scarce unless you make very little and cannot afford to buy it. The scarcity now is artificial, we produce enough food in this world to feed everyone adequately and yet we still have starving poor.