|Like this, only with a HUGE sword|
This question is a unique intersection of crucial information in the campaign.
Are they known gods? New gods? Should they have a selection of Judeo-christian inspired cleric spells? Does their existence explain away literally any mystery in the campaign? Are they not gods, but just powerful humans? Do they dictate right and wrong?
Are you going to have an alignment conversation?!?
On Gods and SuperheroesIn the upper right is a picture of Yahweh, the israelite god of weather (or possibly divine winds) and war. He is a holy warrior, riding a chariot, wielding a honking huge sword and slaying the enemies of the country. His army is a host of stars and planets that smash his enemies. At various times he was associated as married to Anat or Asherah. Eventually, as we all know, he took the place of El, becoming a single god, shedding his pantheon containing thousands.
Clerics were (and always have been!) the comic fanboys of their nations.
They gather in comic book shop temples, gather at huge comic-cons to worship, and war endlessly online with members of other faiths. Can Superman beat Batman? Is the new DC line awesome or terrible? Will the new new DC line be terrible or awesome? (Protip: Don't get hopes up.)
People have always been talking and telling stories about characters that are greater then men are. Is a god popular? Then his legend changes, with a heel/face turn, or perhaps the opposite when they fall out of fashion.
Time passes, and these stories get co-opted by societies, changing as the societies themselves change. Superman goes from being an alien in a human costume to an alien who is a man that puts on an alien costume. Iron man becomes alcoholic in the 70's. Someone important dies. And then they come back to life.
What's popular is what resonates. What resonates is what hero, what myth, represents the struggle of the people.
That's what the cleric is doing. He's reading the latest issue and arguing over it with the other members of the clergy. The higher ups are crafting new stories and tales and altering the old ones for new people in changing times.
The interaction with the pantheon is much the same. A fan of Captain America doesn't disbelieve in Thor. Thor and Cap hang out together all the time. Sometimes they are on the same side, and sometimes they fight. What's important is that you're a fan of Marvel and not those crappy DC heroes.
Clerics in the Game
The above is a perspective that makes the idea of cleric more palatable. And really, that's what we are talking about every time this comes up. Gods, clerics, and holy spells cause logistical problems. If you can heal, cure disease, and resurrect, then do leaders die? Are their epidemics? Does each god have a portfolio? Is that a lot of extra work? Are gods, gods or just beings on a power-level beyond characters? Does Healing magic just waste everyone's time, devaluing hit points as a resource and shoehorning in a character "because we need a healer"? Are armored spellcasters really a good idea?
These are a lot of annoying work-heavy questions for elf-games.
In the games I create, I've eliminated clerics entirely. I also tend to design spellcasters as needing to be much more focused, leading to a "Healing caster" niche for some. Having an unarmored healing caster class as one of over a dozen different specialties means that someone only takes it when they are actually interested in taking the healing role. Other games contain no healing class.
It's possible I'm understating the problems with the cleric. How do the common people react when every god can perform miracles on the street? Open access to an entire spell list? Turn undead neutralizing a whole class of monsters which become overwhelming otherwise? How about their paucity in fantasy literature?
If anyone is already formulating an argument for why clerics should be in the game; you know, stop. Clearly a lot of these problems have been surmounted. Someone wants to play a cleric in 5e, I just hand them the deity list, along with the convenient "additional deity specific" spells. It works. That plus spending hit dice during a rest plus being in the Forgotten Realms addresses most of the points against clerics made above. But the fact that changes were made, shows that it was a fairly common issue for groups to come up against.
Really, the problem isn't surprising, considering the entire class is a reaction to a single player, running around an ancient castle playing as a vampire, causing everyone grief. Nearly half a century later and we're still dealing with the fallout from that.
Get rid of clerics or change them if you want. It can only do the game good.