The good thing is that alignment for all practical purposes is just an optional descriptor much like traits, bonds, etc.. I find alignment a useful starting point for monsters and NPC now and then but it doesn't dictate behavior just gives me a general idea of worldview if I want it. For players? Couldn't care less, thank goodness.For me, verisimilitude comes down to being consistent within your established setting and expectations. One thing I really like about 5e is that it facilitates a number of approaches to this, so that my (relatively) low stakes campaign can work and feel believable, and so can someone else's epic.
And my biggest pet peeve in D&D, in the context of verisimilitude? Alignment. Real people don't have alignments. They are way more complicated.
But that is one of the things about verisimilitude in D&D. Because it's a game, because it's primarily designed to be relatively easy and fast paced, most things are greatly simplified.
Things like HD where people are either alive and fully functional or not is just a game mechanism to make things simple. For me that doesn't have much to do with verisimilitude. It's not realistic any more than alignment. It's just boiling something complicated down to something simple.
Verisimilitude has more to do with the worlds we build and the stories that emerge. We have that sense of verisimilitude when the resulting stories and actions emulate the target genre.
That to me is what is important, thefeel and visuals evoked by the game in our collective imagination, not the mechanical aspects of the game.