Plants give off a pulse when harmed and communicate with each other chemically to inform other plants in the area of insect infestations so they can try to chemically protect themselves. Just because your senses fail to detect the ways in which they express their suffering doesn't mean they are any less able to feel and express themselves than the creatures whose self expression is more readily understood by humans.
(I am a meat-eater, just pointing out something I find funny in such statements)
I believe we may each be using the word "appreciate" with subtly different definitions. I believe it's possible to appreciate aspects of a thing without necessarily collapsing them all into some sort of comparison of perceived total value. I think it's possible that someone who hunts for sustenance might also come to treat the activity as somewhat of a sport, or an art, and so come to appreciate aspects of the activity including the intelligent behaviours of the prey.