Question

All organisms take food from plants. So why we can't said that we are parasites?

Answer 1

We have many more behaviours of a predator than a parasite. Indeed parasites don’t often make a habit of killing their hosts, rather they keep them alive. And in any case we don’t tend to live inside the body of a living host
But we are more than simply a predator, too. We often live in a more or less mutalistic or cooperative relationship with selected species, especially the domesticated ones, or ones we admire in some way.
So we are not totally predator or parasitic we have both the characters