I didn’t draw the line on species classifications, others did that. You seem to be saying that if a subspecies has similar characteristics to a species, then there is no real distinction. No problem. All mammals are exactly the same. Elephant = wolf = shrew. The differences are just a couple of distinctions claimed between the three things, so they’re really just the same.
Likewise, a quartz crystal is alive. It converts sunlight into heat, thus changing energy from one form to another. Under the right circumstances, it reproduces itself. It can be the size of a grain of sand, or several pound’s weight. It can have different colors and structures, the same way that a species can have subspecies that are differently sized and marked. Thus, a quartz crystal must be alive. Unless, of course, it isn’t.
I said no such thing. What I said is that classification is difficult in a continuum. The more history you know, the more difficult it is to draw fine distinctions.
It is obvious, for example, that your family and close relatives share some distinctive features, but as you traverse your ancestry it becomes clear that you are all human beings and are related to everyone else.
In the same sense, humans are related to mammals and mammals are related to vertebrates. The more history you know the more difficult it becomes to draw lines.
I'm not saying all animals are the same, but it is meaningful to say that all animals are related by descent.