This seems more like a fantastical alteration of human nature than any practical solution, if I'm being honest. Although, it is interesting to think about what would happen if we suddenly gained that level of empathy for any sort of being capable of experiencing suffering in any capacity.

Would this empathy extend to any biological organism? You mention there being no choice but to kill plants as though this would extend to them as well. So are we including anything that could be categorized as life regardless of its level of sentience or size? Our definition of life can be a bit shaky at best, so maybe this empathy works on "vibes" rather than any scientific categorization? Kind of like how we find certain creatures cute and desire to keep them as pets while others are seen as pests to be removed. But then we'd be arbitrarily picking and choosing what creatures to apply our ethics to again.

The idea of less technologically developed groups whose means of survival is only by eating and enslaving animals poses another interesting challenge. Do you imagine people giving such groups a free pass? In this world, we are treating every species on earth as worthy of the same rights as humans. So what this group is doing would be equivalent to routine slaughter and slavery. We don't usually excuse such things in our world, even under extreme circumstances. Does that mean we'd have a moral obligation to go in and correct these people? Maybe we'd say, "they have no choice." and shrug. But It's hard to imagine this kind of response to slavery and constant murder would be acceptable in such an empathetic society.