OK, let's for the sake of your argument assume that at this current stage in development, it only supports a dozen enemies on screen at once. But, can we be certain that we will be limited to what we see in this very early build come launch? Certainly titles can get better with development, can they not?
An example.
The Conduit announced:

The Conduit as of a few weeks ago:

So if, IF, the current build is just running with a dozen enemies it's quite possible they are just base testing models and not resepctive of the final product.