I'm guessing they removed the creatures to make it less campy and more serious... or they were just lazy, treating it as a demo for future RE remakes.
If the excuse is less camp, they are about twenty years late since RE has always been campy as fuck and that's what makes it endearing. But even still, giant spiders is such an easy scare for most people considering how it's a common phobia. Imagine with the lighting and good looking graphics how terrifying they could have made it, hearing them skitter all around and causing you to whip around with your flashlight in paranoia, would've been so good. The webspinners/Black Tiger in REmake worked very well and looked like beasts.
But if I had to guess, they'll probably include the missing enemies like crows/giant spiders in REmake 3 to show "Capcom listens to their fans" or some shit like that.