As we know where 3 Catholics are there are 4 opinions about politics, 5 opinions about proper roleplaying systems and 7 opinions about details of molinist-thomist controversy.
Now this board is truly doomed.
As one of the Catholics here, I definitely add to two of the three (politics outside of RPG matters being off limits to the main boards).
In the case of the D&D Cleric, I haven’t really been comfortable with it since D&D went from the standard of having undefined celestial powers by default(such as described in the Red Box) to pushing its weird brand of henotheism with specific gods, and I generally consider the Forgotten Realms to be a theological horror show (which is why I am largely unsurprised it’s been made the default setting by the Godless Left).
Frankly, I think the biggest mistake made with the D&D cleric was the addition of the Paladin class which pretty much entirely consumed the original concept of the cleric as martial holy crusader and caused cleric to need to be redefined (which is where the idea that they’re just “priests” started to develop because they were no longer the holy warriors). The second biggest was making vancian spells out their miracle working.
The way I largely get around these matters in my own setting is that, first, there is a notable difference between ordinary NPCs with the Religious background (i.e. you normal priests who number about 1-in-100 in the general population, most of whom don’t even have magic) and the Theurge or Mystic classes who are rare exceptions with combat capable magic (c. 1-in-10,000).
Second, the setting supports expeditions to pre-Cataclysm ruins as boons to civilization (vs. selfish profiteering) and, unlike the WotC-era D&D, has options which actively encourage bringing companions and hirelings as part of the expeditions even at low levels. A priest being sent along on a months long expedition of twenty men seeking to recover lost knowledge for the benefit of civilization to see to their spiritual needs isn’t nearly so strange when you consider that priests also participated in various real world expeditions of discovery (and even military conquest... hence Chaplains*).
Third, I spent time with the primary astral religion to develop various martial orders within the larger faith; ex. The Scribes of Verax (who despite the name are more like Indiana Jones plumbing the depths of ruins to recover lost knowledge), the Templars of Bellos, the Knights of Viatus (forge and protect travel routes in the name of the god of travel, hospitality and commerce) or The Order of Venetrix (hunters of the undead).
Related to that was the decision with the elves to go the priest-king route and unify the aristocracy with the religious hierarchy. Thus, the priests are, by default, also warriors who lead their houses into battle.
Finally, The Old Faith very much runs on the Old Testament Prophet and Judge model where they wander where God leads them and beating occupying Philistines to death with your supernaturally gifted strength and the jawbone of an ass or raining down fire on Jezabel’s priests is a thing.
The PC class associated with that religion (the Mystic) has as its basis that you didn’t choose the power, The Source chose you to wield it. Other people could engage in the exact same practices and never receive the gift, others are born with it having never done anything to earn it beforehand. The only commonality is that they always find themselves in situations where the divine gifts will be needed for the good of others.**
But in terms of fixing D&D, I’d start by merging the Paladin back into the Cleric and then add an NPC class akin to the 3e Commoner, Expert and Warrior just to make it clear that Clerics are NOT the average priest or anything close to it.
* The position of Chaplain itself grew out of a military tradition of having a priest carry a holy relic (originally the cloak of St. Martin of Tours... chaplain meaning “cloak bearer”) into battle so as to carry the favor of God. The priest didn’t fight, but rather like Moses holding his staff aloft, was believed to have provided the men with supernatural assistance in battle. For a while my concept of a priest class in my system actually made their primary class feature “mantles” - auras of divine power that buffed allies or hindered enemies which the priest directed during combat (giving them something tactical to do without needing to engage in violence themselves).
** basically, Mystics are ALWAYS PCs or named NPCs; 1-in-a-million men/women capable of performing miracles. And because there’s no way to either aid or restrict access to the power like the formalized astral pacts (the magic of Theurges) or arcane study (the magic of the Wizards) it’s also the most feared among societal elites.
Restrict access to weapons and armor and any Fighters will be hindered compared to your professional soldiers. Keep the population uneducated and no Wizards or Gadgeteers will arise among them. Restrict the knowledge of the proper ritual forms and you’ll never fear a Theurge rising to make trouble. But a Mystic can come from anywhere; anyone of any station might arise at any time with the power to challenge any you’ve gathered for yourself.