You actually didn't kill too many grues in the Zork games. Maybe none. You just shone a light on them, and they scattered. Here, you are a hungry grue, tracking down adventurers before you starve. There's no standard map to this game. You need to use your senses. It's a timed game, as you starve if you wait too long, both overall and at the final conflict. But there is also nothing wild to do, or any intricate puzzle.
Sight is not one of them, of course. You start with your eyes closed, in your layer, and if you open your eyes, you lose your other senses: taste, feel, smell and hearing. All four of these are used as you stumble through caverns. There's some trial and error here, but the main thing is, if you use certain commands twice, the adventurer is alerted to your presence. They may flee or outright kill you.
It's a sparsely described game, with a tense if quick hunt. At the end, you corner the adventure, and this is where I hit a wall. Some deaths were expected--you didn't prep yourself enough, or you used the same sense twice. But the final one, I just assumed you used one verb first, and I kept trying to find ways to make it effective. (There is a preparatory verb. It makes sense.) I didn't think of skipping over a certain step. There's some cluing here, as the game asks you if you want to, before the adventurer kills you. If you manage to get to the point, though, you have a meal!
Grue is clearly well beyond Zork: a Troll's-Eye View in terms of realism and description and character development. It's fairly quick to go through. I suspect it slid down the rankings due to the guess-the-standard-verb frustration at the end, as well as some other things which seemed like beginner mistakes. However, I recognized the author's name from some Apple II programming groups, so he is no beginning programmer, and he was probably just blindesided by stuff he could fix easily once he knew about it. Inform can just be tricky that way. It's a good idea and worth playing, and it's quite surprising someone didn't do it sooner. It feels like it has some holes that could be fixed pretty quickly. But all the same, I'm very glad it's there. There are a lot of Zork tributes that rely on canon knowledge or are just another treasure hunt, and this is genuinely different.