I think it’s mostly an observation about unforced discontent, which is a notable (defining?) feature of human existence that’s apparently (at least) much rarer in the rest of nature. I doubt people much closer to nature, death, and killing than most modern OECD-state humans weren’t aware that animals suffer, nor that they must sometimes run to catch their food.

It might be worth interrogating the original language of the work, which I’ve not done. The translator may be depending on the reader’s cooperation here.

I do think that’s true, but largely because animals mostly don’t have the luxury of being out of survival mode. They can’t have unforced discontent when it’s constantly being forced.

I’m sure the ancients were aware that animals suffer. I think it’s noteworthy that the passage in Luke was talking about plants, not animals. It’s hard to imagine effort and discontent in an organism with no brain.

In any case, I’m definitely not taking life advice from an apocalyptic cult telling me not to plan for the future and give away all my possessions because their god will provide.