There are lots of species IRL that can see better than people in dim light... which ones see in complete darkness? (5e Darkvision gives both, right?)
This is my only beef with Darkvision. Mechanically it’s
fine if you actually apply disadvantage on perception checks to see (and therefore -5 on passive perception), but it bothers me from a verisimilitude perspective that it allows you to see anything in total darkness.
I think the real problem though is that 5e treats “outdoors at night” and “the confines of an unlit dungeon or subterranean vault” as the same level of darkness. An owl could see pretty well in the former, but not at all in the latter. On the other hand, I understand wanting “outdoors at night” to be darker than “the soft twilight at dawn,” which intuitively doesn’t seem like it should be bright light.
Maybe the solution is to treat
total darkness as a third category of lighting, in which magical darkness and lightless caverns both belong. Darkvision works as-written as long as there’s some small source of light in the area, even if it’s not enough to bring the light level up to dim - stars in the sky, a soft flickering through the crack under the door, a little patch of bioluminescent fungus, etc. In
total darkness, there’s no light at all, so even creatures with Darkvision are effectively blinded (unless they have Devil’s Sight). Then the effect of the Darkness spell is simply to create a patch of
total darkness in the affected area.