First and foremost, as with any IF work, the idea of agency should be taken into consideration. Your choices have rationale, and when you execute these choices, they make significant impacts.
In this regard, Eternal does this task well; characters may not even make themselves apparent in differing timelines, and more often than not, they succumb to the ravages of time without your involvement in their own personal stories.
So if you come to this story with the idea that you'll be making drastic changes to the world, you'll have your expectations met.
It's also important to acknowledge, however, that unlike IF works that cast your character as a blank slate, the character you play as is preset for a certain disposition. The summary description and exposition you get early on paints a fairly bleak picture, and if your torturous training is any indication, it's that your character isn't going to be much of a hero.
In the regard that your character is not much more than a physically strong person, the story conveys your limitations decently well. It doesn't mean that you won't run into a lot of unexpected deaths and outcomes (thankfully, CYS allows backtracking), but even on paths of failure your rationale is entertained. Hardly any more or less fair than a Goosebumps, really.
So you have a somewhat darker fantasy story (not quite 'grimdark'; you're not beset by an endless amount of world-ending enemies) that has you well-positioned to survive, and at some points thrive. Are there any great truths about character or morals that reveal themselves? No. Do you get to enact a lot of badass violence like one of those 80's action flicks? Yeah. Do you have entertaining dialogue and character dynamics that break expectations? If you're used to more tame works, definitely.
So with all this in mind, Eternal is above all a fun read. It's not going to revolutionize how you view and treat people, and it definitely prefers long-term attitudes you develop from the rationale of your choices; the outcomes of those behaviors you give the main character pan out in varying levels of success. It's a work meant to satisfy and entertain, and it does this well...provided that you don't take the edge too seriously.
Yes, this game IS the sequel to Innkeeper (although it stands on its own two feet well enough to not need more than a hint from its predecessor), but the exploits of your main character here does a lot more for storytelling and worldbuilding.
Rather than start off with the obligations of running a family inn, Rogues starts you off with absolutely none; as a the titular rogue of society that you are, you're given plenty of options and opportunities to invest into once you get kicked out of your hometown. While I can say that one of the choices is severely under-developed (it involves you arriving at a city thriving on slave-trade, but it ends before any real exploit can begin there; EndMaster did say he would return to expand that), the others are fleshed out enough to give you several hours of odd jobs, organized crime, and the odd politicking here and there.
It's just as gritty as Eternal in regards to the violence factor, but it doesn't quite become visceral enough to become a gore-fetishist's dream. Likewise, it's nowhere near optimistic enough to have every character survive in a single path; you'll often be met with people with opposing ideals, and depending on the choices you've made, you can be their closest confidants, deadliest rivals, or a mere spectator watching their hopes and dreams shrivel up in flames.
Fortunately, the author has (relative to his other stories) balanced out more of the choices to reach real endings unlike some ambiguous cliffhangers in his other works. As a result, much of what you do will end up in varying levels of success, and the many roads you do end up taking often bring you to places of prestige, power, and on particularly fortunate routes, glory. Not all epilogues feel especially great, but none of the epilogues feel especially bad either.
And for the common, no-good thief that you'll start out as, that's good enough for the story to feel fun, in its own fucked-up sense.
Taking inspiration from the Wasteland series, Fallout Series, and others, Ground Zero is exactly what you'd expect from a post-apocalyptic CYOA, and that's not necessarily bad.
Different branches lead to different adventures varying from survivor-on-survivor squabbles to city-sized sieges, and although the routes to get to these different scenarios aren't exactly obvious at first glance, the tired cliché (among others) of a one-man-army in the apocalypse aren't entertained too much; most heroic (and suicidal) antics get you killed fairly quickly, and the ones that do keep you alive are best left to more ambiguous fantasies for you to live out off-screen. To that extent, even sudden losses and dead-end branches give you a sort of grounding to reality while the conventionally less-explored ideas (like becoming a mutant) get much more air time.
If surviving in a whacky, sand-filled world without dealing with the clutter of video games sounds like something that would pique your interest, this CYOA is it.