It's probably the most realistic game I have ever seen because the level of interaction from everything in the game is ridiculous. Not only is the scenery alive, but so are your enemies. In your typical video game, your enemy is static and emotionless, and you can tell that easily. But in The Last Of Us, your opponents act like actual human beings... Sometimes you even think twice about killing them and you even feel sorry for them.
You needn't take most of this post as a direct reply to yours. Now then: one's opponents in a survival game still aren't human for as long as they remain definitely opponents. The AI is demonstrated to be fairly realistic in the mode of being hostile, but the one thing it apparently lacks is being potentially friendly as humans can be. One ultimately can't be remorseful about killing in a game when that is their only given course of action. If the player could, say, upon approaching NPC groups declare themself friendly, a brief standoff could give way to either amicable conversation or shots being fired; you can't know unless you try, but if you can't try as per what we see from the demo then I am ultimately seeing nothing but an action game. It lacks the natural elements inherent to survival; there could be choices to make, fight or flight essentially, but the player isn't given such options. It could be very tense with AI reactions to the player's presence somewhat randomly generated, but it seems one just fights their way through the city. Then of course with it presumably being a linear game, I doubt the need for life's basic amenities will be significant at all.
That said, I can't look down on what is shown of the game's combat aspect, assuming none of it was scripted. I just think that the game leans so heavily into combat that it will certainly not be 'genre-defining' and probably won't involve surviving much more than enemy attacks in gameplay. All should note how no survival-ing occurs in the demo, besides the NPCs searching the building which isn't within the context of the game engine anyway (what I mean is they won't actually benefit from their supposed action, it's just a simple pretext for their location when the player encounters them; compare this to STALKER wherein NPCs will loot bodies, acquiring and potentially using their new items for the exact same purposes the player can and then some, ex. medkits to heal their friends).
I know — I'm disregarding what the game's story might entail, but that's just me, I generally don't play games for their storylines.