I just read the thread about this (thanks @Christy!) and had a couple thoughts.
One, it’s my understanding that the Garden was a physically separate place from the rest of the earth, right? And there were animals both in the Garden and on the earth. But there was only a Tree of Life in the Garden. And the Tree of Life was what would have allowed Adam and Eve to live forever if they’d been able to eat of it, right?
Therefore, how could the animals outside the Garden have been expected to live forever? They didn’t have a Tree of Life. So it was expected for them to die.
(Incidentally, did the rest of the animals get kicked out of the Garden too? Or are they still there?)
But back to Gen 1:30. The context that I think is really interesting is dominion. 1:28 reads in part, “fill the earth and subdue it, and have dominion over the fish of the sea and over the birds of the air and over every living thing that moves upon the earth.”
So humans have dominion over the earth (day 3) the fish and birds (day 5) and the animals (day 6). Also in the next sentence God gives them the plants exactly as they are described on day 3. And then he also gives the plants to the beasts and to the birds.
Where else in Genesis is dominion assigned? On day 4, the sun and moon are made to rule the day and night which God made Day 1. But they are also “for signs and for seasons and for days and years,” and “to give light upon the earth.” It is their job to facilitate life for the creatures on the earth.
On day 5, sea creatures are assigned to “fill the waters in the seas” (waters are day 2/preexisting but seas are day 3) but not to subdue them.
So where does this leave us? Day and night are ruled by the sun and moon which are for signs, etc. (to humans for sure—probably also to beasts and plants). The seas and sky are filled with creatures, the earth is filled with plants and with beasts that are given the plants, and to humans are given the earth and the fish and the birds and the beasts and the plants. This is an incredibly strong statement of human importance!
(What was God thinking?!?)
Anyway, I don’t think strict vegetarianism was the purpose of the text or what it was trying to convey. Although I could, of course, be wrong.
ETA: Which is not to say we would not all probably be healthier if we ate more plants.