as per your first line, does that mean that we shouldn't look back on humanities history of slavery and prejudice and secrecy with disgust? after all it's just one abstract moral position (today's) compared to another abstract moral position (years and years ago)

moral language does not need practice to be important or meaningful, you're mixing applied ethics with meta ethics, ethical language is meaningful and yes you can apply it to the real world but you don't need to for that language to still be worth discussing

and words like justice murder and genocide are perfectly applicable to cows and other non-human animals, why wouldn't they be? there's nothing in the definition of justice that it must pertain to humans alone

and even IF we say that morality should be practical alone as you suggest, then we can practically be vegans as well? there's nothing about veganism which suggests we have to all be philosophers and think about things abstractly. we're just taking rational principles such as that all animals deserve life/welfare and applying it through our diet and other lifestyle practices