The mechanics of this are a little fuzzy, as it involves characters who gained their powers through accidents and circumstances, like The Flash, The Atom and Plastic Man, as well as those whose powers are natural abilities to their alien species, like Starfire, Martian Manhunter and Superman. With the world's greatest heroes sidelined, it's up to second- and third-stringers with technologically-based "powers" like Steel, Blue Beetle and Booster Gold to help fill the void, although some technologically-based powers did fail, like Kyle Rayner's Green Lantern ring.
Best not to dwell too much on the specifics of event, as Moench doesn't, and certain questions are addressed only in passing ("What about the supernatural geeks? Spectre, Dr. Fate, Zauriel..." Guy Gardner asks in a splash page, and The Atom answers "All among the missing-- Or at least no one's heard from them." And that is that for the magical heroes, although I guess it's worth noting Captain Marvel and Wonder Woman are also left powerless). At any rate, it's never explained—beyond the title—and its "rules" are only evident in what occurs on the pages.
The tagline for Elseworlds is that "In Elseworlds, heroes are taken from their usual settings and put into strange times and places—some that have existed, or might have existed, and others that can't, couldn't or shouldn't exist." This is very much a shouldn't exist kind of story, as it shows some of DC's greatest heroes in spectacularly bad lights.
Before we get to that, though, I should note that this story is very much my particular jam, and few things in comics excite me as much as the sort that occurs on the story's 19th page, in which we see the JLA Watchtower crowded with some 30 heroes in a single splash page. Many of these heroes are just making one of several cameos in the story, some of them won't appear again at all, but man, I just like seeing, say, Red Tornado and the android Hourman standing shoulder to shoulder and imagining what they're talking about, or just getting a little reminder that Damage exists, you know?
Pencil artist Dave Ross, here inked by George Freeman, has a great style that is quite well-suited to this kind of extremely sincere, often melodramatic (or, perhaps, soap operatic) superhero story, the characters all looking like themselves and seemingly perfectly captured when in action, but also showing a great deal of emotion and "acting" when they struggling with negative feelings or baring their souls to one another, which they do a lot of in this (There were certain panels where the Ross/Freeman team evoked the work of Rags Morales, a favorite artist of mine, if that helps you place the style).
The other fun thing about the story is that it foregrounds several then lesser-seen characters, like those mentioned previously, as well as Guy Gardner and Supergirl (Moench splits the attention between the core JLA members reacting to their lost posers and the tech-based heroes who must replace them, rather than focusing too much on the heroes who never had any powers or super-tools to help them like, say, Green Arrow or Arsenal or Black Canary; they mostly just appear in a handful of cameos).
Wonder Woman is similarly distressed and gives up trying to be a hero, instead getting a job on Wall Street. She turns to (Christian!) religion and, sometime after her break-up with Superman, even considers suicide.
Kyle Rayner, who gets beat up by Sonar II, spends the entirety of the story ranting and raving and throwing his ring around, never consulting with the other Leaguers, and he eventually works a heavy-bag until he feels he's ready to beat up Sonar II with his bare, ring-less hands.
This being an Elseworlds, I guess it's acceptable that Moench chose to highlight the darkest, bleakest futures for some of these heroes, but, well, they don't come off as all that heroic.
It's not hard to imagine any of the three either finding fulfillment in their normal lives—I mean, as a journalist, husband and son, Clark Kent has a lot going on whether or not he's secretly Superman or not—or continuing to fight crime without their powers. They might not all be martial artists and gymnasts on Batman's level, but all of them, especially Wonder Woman and Superman, have been fighting people on a daily basis for years. It's not hard to imagine Superman taking up a jetpack and a ray gun and continuing to protect Metropolis, or Wonder Woman grabbing a spear and shield and fighting crime the same way Black Canary does, you know?
These heroes are contrasted with "The Phoenix Group," made up of Flash Wally West, Supergirl Linda Danvers, J'onn J'onnz and Aquaman, who all decide to train under Batman and Robin before adopting new heroic identities under which they can fight crime using fighting abilities and gadgets. They become, respectively, Red Devil, Justice, The Green Man and (sigh) The Hand.
Ultimately they save the day from Lex Luthor, who seeks to take advantage of the new, power-less world by mass-producing super-suits like Steels and trying to jumpstart super-powers through genetic research.
It's a fun enough story, despite the bleak portrayals of some of the characters as they spiral downward—don't worry Superman and Wonder Woman get their lives back together, and Kyle does eventually beat up Sonar II, but at the cost of his own life—and some extremely, funnily purple prose from Moench, which reaches its most overblown when Superman describes to Lois how he felt during his initial power loss.
I certainly had fun discovering a "lost" story from a point I was perhaps most engaged with the DC Universe as a setting full of characters I genuinely liked.
Despite the struggles the fictional DC Universe had in the wake of the event here, the real world DC Comics would probably be pretty much a-okay without any super-powered heroes...although I bet they'd give Superman a jetpack and some super-weapons to continue his never-ending battle, powers or no powers.
*Which was collected along with the infamous 1999 Elseworlds 80-Page Giant and Randy and Jean-Marc Lofficier and Ted McKeever trilogy of German expressionist film-making inspired books Superman's Metropolis, Batman: Nosferatu and Wonder Woman: The Blue Amazon in 2017'a Elseworlds: Justice League Vol. 2, which is where I read it.
**In fact, the premise is somewhat similar to that of John Byrne and Ron Wagner's 1997 Genesis, in which a receding "Godwave" removes the meta-human abilities from many heroes and leads to a weird "crisis of faith" among ordinary heroes who have no superpowers. It was pretty terrible, though, and my very least favorite of any DC crossover event ever.