In most of the cities within the post-apocalyptic world of 3 Generations After the End (3GATE), the priests rule. These are very different men of the cloth than we see in our current time. These priests do not revere an unseen god or the words of prophets translated from ancient tomes and scrolls. Instead, they worship the remnants of a once great society, pulling words from PDFs of technical manuals on computer tablets.
In most fantasy tabletop games, a priest or cleric, is very different thing from our techno priests. In D&D, clerics are warriors of their god, able to wield divine magic to smite foes. It’s a very different style, and you have some choices to make as a group if you want to include these classes as an option for your players. By default, there is no divine magic in 3GATE. The apocalypse brought back the wizards and witches of old, but not the gods.
The easiest way to deal with divine magic is to ban it outright. That means no paladins, clerics, or oracles, at least not in the mechanical sense. Instead, these characters would take classes like engineer, artificer or alchemist. When they step into battle, no godly force intervenes more than the advanced technology that only they seem to be able to master.
In this way, a priest could appear very differently depending on the tech level of the city he hails from. I imagine something like Carl from Van Helsing, wearing simple brown robes, and then pulling out clockwork rifles, and numerous wondrous items created from astounding future tech repaired into new uses. On the opposite end, a priest from The Keepers of Syrinx might dress in a perfect suit, accessing databases remotely with nano-implants, and calling laser strikes down from satellites. Either style works, and there’s no reason why they can’t exist in the same campaign.
Which brings me to the other way to run things, and the point of the opening quote: Allow divine classes, but play all their abilities as the result of technology. A searing bolt spell is really a wrist laser. Healing with a Lay on Hands ability isn’t the work of the gods but advanced ointments or bio-repairing nanobots. Even a pillar of divine fire doesn’t need to come from the heavens but from a satellite, or a tossed vial of properly mixed chemicals. The priest might understand the technology he works with, or he may only know the ritual of it all and really believe it’s the work of the gods. The gods did, after, all give the priests the holy texts to tell them how to accomplish these miracles. Like any good technology, some people seem to be naturally gifted or have a calling. Then again, sometimes no matter what you do it just won’t work until someone breathes on it the right way. Sounds like the work of gods to me.
There’s no need to make it all one way or the other. Perhaps the re-fluffed divine characters only come from the more advanced cities, or represent those that are naturally gifted in understanding technology. They may be in the same party with another priest who is just as devout, but their technology equates to only to a few special items, and play a fighter mechanically. These differences can give depth to your world, as long as they retain links to each other. It shouldn’t look like whole different worlds happened to be next to each other for the sake of the adventure. Make sure some things carry over, even if its just a few symbols, sayings, and beliefs.