I took the cleric and paladin classes out of my game because I felt that a character turning toward a religion was something that should happen during play. That moment that a warrior defends a temple and holy light shines down on them and they receive Pelor's blessing is too good to be passed up as mere "backstory." That's the meat and potatoes right there, not the appetizer!
A mortally wounded adventurer is carried into the hut of an old hermit woman, and as she prays over him, he sees a vision of Elhonna calling to him, telling him she needs him to spread her teachings. It's his destiny, which if not achieved, would yield terrible consequences. Boom, cleric (or missionary) origin. It has a sense of urgency and reality, rather than the distant and ephemeral relationship most cleric class members have with their deities.
This game decision was extremely freeing, because now religion didn't have to be part of the campaign if I didn't want it to be. Sure, characters could be religious, but unless I chose so, no divine powers (and thus near-direct deity involvement) would be required. Pantheons take a long time to make, man. Sometimes I just want murder-hobos fighting dragons in a godless hell-hole, but as soon as any divine class is allowed, there is an entirely new dimension to my world that I need to fill out, whether it will be used a lot or hardly ever.
Not to mention, NPC members of religions also got toned WAY down, so that they are nearly all mundane people with regular reasons for being religious, rather than magically gifted healers who can be the deus in your deus ex machina plot problem. AND a great corollary to this is: magic healing is much rarer, therefore the game feels more dangerous. May not be your thing, but it is so my thing.
This train of thought led me to arcane magic-users, M-Us, or "moos" for short. A moo is basically in the same boat as a cleric or paladin: they have some supernatural ability that everyone wants to know more about, but the narrative drive it creates is crippled by the game always beginning en media res of their development. A moo's first experience with magic is a defining and contextualizing moment of unprecedented importance in the story, but when it is resigned to the backstory, it matters not at all.
So, you can take moos out too, and make magic exactly like religion: you get it during play, if at all. Again, the freedom this offers is immeasurable. Now, if I don't want to incorporate pact magic and patrons in my game, I don't have to worry about a player choosing the warlock class. It also means magic (and religion) can be totally mysterious and not balanced, because it's all in-game development. It puts the risk-reward balance in player character choices, rather than character creation. No need for spell slots, no need for domains and specialization rules. Just cause and effect story.
Each spell or magical power is its own rule module with its own limits and costs and risks. If you want a bigger/better/cooler/flashier version of what you have, you can't just kill stuff until you level-up, you have to go out in search of the better version and learn how to do that. But be warned, it may have costs you are not willing to pay, or be on the other side of a challenge you are not ready to face.
Not having any set rules for how magic functions allows you to try different things for each moo, like magic atrophy, crude magic, modified vancian magic, wizard garment restrictions, a panoply, i.e. collection of magic foci, or the spell components you've been ignoring your whole life.... And so much more!
But wait! Won't these magic systems spin wildly out of control? Won't my moos either become gods among men, or slump over and give up because the costs of magic are too high and not balanced with the real classes?
It's all in how well you DM, of course. But rest assured, your moo isn't just a moo, he is also a warrior, or a dwarf, or a scoundrel, or some other mundane/race class first. Not all D&D characters live beyond their first couple adventures, and not all moos ever get to cast fireball before blowing themselves to smithereens in a magical mishap. All game systems have edge cases that screw things up. You deal with them as they come along. But at least with in-game magic only, your players (and you, to some extent) get the excitement and mystery of magic back in your campaign.
Players now have to actually choose whether gaining magical power is worth the risk. Parties now have to gather information on their sorcerous enemies before charging in, or risk death by unanticipated magic abilities. Playing a moo well now requires learning and exploring above all else, and especially above choosing the best spells at each level.
This fantasy RPG hobby of ours is about three things. First is being with friends, and what system you play should have no effect on that. Second is exploration of a magical world. If gaining magic is part of exploring, rather than part of the rulebook, then that's just more exploring to do. Win-win. Third, tabletop is about problem solving in a more dynamic and complex environment than any video game or board game can model. If you make magic a problem to be solved, and a challenge to be overcome, rather than something characters are just handed from the get-go, then you have all the more material to work with as a DM.
Until next time.