Still, it's a big chunk if optimized right. Games seldom use more than 2-3GB or RAM for CPU cache, so they should still have 2-3GB free for GPU which is okay for 100p. Source on PS4 operating system eating 3GB, as that sounds like a lot?
2-3 GB off GPU is only "OK". To get really good graphical effects (say 2K on pretty much all your textures and 1K on normals, (all optimized) plus parallax, etc.) and the ability to smoothly load additional objects as the character moves around, you need more like 4K plus the ability to offload VRAM to RAM - or at least that has been my experience. Of course there could be further optimization to enable you to do more with less hardware (and I'm sure they have tried to take advantage of the latest and greatest techniques), but each further increment of gain from optimization gets more expensive in terms of developer labor.
Still much of this gnashing of teeth may be premature. Much of what has been seen are YouTube videos, which themselves often have serious video quality constraints due to downloading issues, on YouTube's platform, and which suffer from degradation while being recorded due to the overhead needed to capture them for video streams - or at least this has been my experience - I can often get better looking graphics on inferior hardware compared to what someone has uploaded on YouTube. Comparing static screenshots is kind of pointless as the effect we (or I) really care about is the overall dynamic video effect in game, not the detail of a single screen shot.