It's long been a truism that gamers dislike playing clerics. Most clerical PCs are the result of "We have to have one of everything" / "We can't adventure without a healer!!!" mindsets. The people who play them, more often than not, are the weary volunteers, the folk who showed up late when it came time for chargen, the ones who were bullied or browbeaten into it, the ones for whom it was Their Turn To Play The Cleric.
A couple factors go into this. Some claim it's because the world is becoming atheist, but I don't buy that: certainly in America, the notion that religion is less dominant than it used to be would be farcical, and the trend from the 70s on forward -- the entire history of the hobby -- is for the United States to become more religious. But there surely is a marked nervousness about the concept in RPG circles.
This is, in fact, nothing new. RPGs have always, generally speaking, sucked at depicting religion and faith. Part of this is the OD&D dungeon fantasy mindset, where it was important to know what level your cleric was, what nifty magical toys he had, and oh, of course, what alignment he was, but pesky things like doctrine, dogma and ritual practice were afterthoughts at best. I had more than one conversation in the Seventies with players of D&D clerics where they could rattle off all the stats and items, but were shaky on the names of their gods ... except that, of course, the anonymous gods in question were "Lawful Good!" In the game that Gygax built, clerics were just a different type of fire support unit.
Beyond that, the bewildering array of deities most fantasy campaigns and settings had, combined with alignment, contributed to a bulletpoint view of religion. Sure, the Sea God's about water, uh-huh, uh-huh, and sailors worship him, uh-huh, uh-huh, and, like, dolphins are his messengers, uh-huh, uh-huh, and, well ... alright, alright, he's Lawful Good! Okay??? Nothing about doctrine. Nothing about history. Is the clergy celibate? What does a wedding service look like? Are they in favor of slavery?
We never knew those things, and since there are twenty other gods, each with their sets of bulletpoints, we don't have any traction for what any other god is about either. Three gods, sure, we could get a handle. Thirty, and who can be bothered? Nope: it comes down to "Bunsgrabber is the God of
Partying Down. His alignment is Chaotic Horny. He is depicted as a
young man with a great tan, wearing cutoffs of purest gold. His priests
always wear sunshades and strange caps with horizontal visors pointing
backwards, and his High Temple is at the coastal fort of Lauderdale."
Beyond that, since there's a strong streak of distaste in some circles for any roleplay that gets in the way of tactical planning and execution, we can readily see where the conflict comes ... the more so in that cleric/paladin types in D&D and other such games are portrayed, more often than not, as humorless scolds blending the worst of medieval Catholicism and the Inquisition. Their faith never does seem to benefit the party ... the only impact it has is "Damn, we can't do X because the cleric will go into a tizzy."
There are ways to mitigate this, above and beyond the extensive advice I give in my Starting From Scratch: Faith Manages post:
* Slash the number of religions in your setting. By a lot. A half dozen is about what people can handle, at maximum. Campaigns work fine with three faiths. Or two. Or even just one.
* Develop those religions. What do they believe ... comprehensively? What are their practices? How are they trained? What does the hierarchy look like? (And please, how about we not just parrot the Roman Catholic church?) Is there any similarity in temple architecture? What's their take on icons? Do they allow group marriages? Do they trouble over marriage at all? Give the players some meat to chew, here.
* Consider that in sharp contrast to how most GMs portray a polytheistic society -- as, in fact, henotheistic, where people worship only one god but ignore the others -- make it a genuine pantheon. It doesn't matter if I regularly attend services of the Sea God; if my daughter's getting married, I'm going to make sacrifice to the Fertility Goddess. I might recite a rote phrase to the Fire God when firing up my hearth. I'll surely sacrifice to the War Goddess before going into battle.
* Remember the posts where I talked about mages, and that the vast majority of them are going to be researchers, academics, in service, carrying out official duties and the like, as opposed to being enchanters doing nothing but churning out goodies-on-demand for PCs? The same thing with clerics. Priests should not be doing nothing but lazing on barcaloungers at their altars waiting to heal PCs. They should be working on sermons and homilies, or in long prayers that can't be interrupted, or in the middle of holy ceremonies, or managing their parishes, or performing pastoral duties ... or off healing their parishioners. (Seriously, I'm much more likely to have burned healing spells on my parishioner Rolf the carpenter, who just fell off the damn roof, or on his wife, who's having a rough time giving birth, or on their teenage son, who fell into the damn hearth and got badly burned trying to get Papa's supper going, than to be hanging onto them on the off-chance non-faithful adventurers wander by.)
* Turn off the god tap. Seriously, folks, faith ought not be a public utility. If you're not a worshiper of my god -- or at least pay lip service thereto -- my healing powers ought not work on you. If I'm a white light priest in a party of murderhobos, my powers ought not work at all. But, by contrast, if you roleplay some serious faith, perhaps the local priestess of the Fire Goddess should see that, and be more favorably inclined to you because of it. Give people some incentive to do this. A character makes an act of devotion: attending a service, reciting prayers (the whole thing, not "My character recites the Creed of the Sea"), lighting devotional candles ... fair enough, the character gets +1 for the next important roll.