Hmmm, the wheels are spinning... spitballin' on a Wed. afternoon... for a possible framework for lessening spell dependency of certain casters and differentiating caster types...
Mages, and other magic-users who access Arcane Magic spell lists learn/study/practice their spells. The standard spell progression we know. Casting mech's are basically the same. Spell levels 0 (cantrips)-thru-8. Cantrips are still at will. Intelligence is still the casting ability. Except for cantrips, which have no limit, you may only ever learn/know/have as many spells, per spell level, as your Int. modifier + Prof bonus. Specialist concepts: Illusionists, Conjurers, etc... operate by this method as well, with slightly different class features and individual spell lists. They have the same cantrips and unlimited access to their spell lists, but can only ever know Int. mod. spells that are not on their particular specialist magic list. Illusionists, for example, will have all of the same illusions, enchantments, some conjurations, that the general mage can know, but also have other illusions, enchantments, etc... that a general mage would never get access to. But things like Magic Missile or Fireball would be outside their spell list and so, require taking one of those limited spots.
Clerics and other magic-users who access Divine Magic spell lists channel holy/positive (or unholy/negative) energies. Their spell use does not kick in before 3rd level. They receive a more limited spell progression - their lists only go to/through 6 circles. You have access to all spells of the 1st and 2nd circle. Cast them as needed with your available channels. Beyond 2nd level spells, you know only those you select, cast with your channels, "Spells known" casting, in the 5e vernacular, specifically granted magic. Channeling different powers and bonus/domain spells form an added "final" circle of magic, giving them the divine number of 7 tiers of magic, all together. You number of channels per day is bolstered by your Wisdom modifier.
Druids and other magic-users who access Nature Magic spell lists attune and intuit to the primeval energies and mystic ways of the natural and physical world. They have a spell progression that begins with cantrips, but then only progresses to 6 spell levels. You know all spells on your list but are limited by your slots, as most casters of arcane magics. Additionally, they know how to invoke (channel) the spirits and powers of the elements and natural forces to channel magical effects upon themselves: moving unseen, tranforming to beasts, opening pathways to the land of faerie, etc... Your Charisma modifier is added to your spell slots per day.
Psychics and others who may access Mental Powers lists draw power from within their own expanded or enlightened minds, bizarre bloodlines, and/or awakened souls. They use a power point system that fuels the manifestation of their powers that range from "0" point cantrip-style abilities to powers equivalent in power to 8th level arcane spells. Your Int. modifier adds to your daily points.
Warlocks and others who may access Mystic Powers lists draw power from an external, non-divine, source: a powerful magical being (fae , demon, dragon, etc...), cosmic force, universal ideal (alignment), or some combination thereof. You use a power point system to fuel the manifestation of the powers you are granted by your source (or siphon from the cosmos or absorb through some mystical connection). So you have a list of specific powers(features) that you channel and set spell slots, with specific/chosen "spells known." You receive cantrips (usable at will) at level 1. Other spell progression doesn't kick in until 3rd level and doesn't extend beyond 5th level spells. Your additional magical powers are granted by your source to give powers/access at higher levels to chosen singular effects equivalent to 6-8 level spells. This model would produce those who are "magical" primarily with/due to supernatural powers, and spell use is a secondary or tertiary consideration for the class. Warlocks (the arcane) can still spam eldritch blast and receive patron flavor powers; Bards (the nature) still inspire/bolster allies and enchant foes; Paladins (the divine) still smite and have invoke combat bonuses and defensive auras; and Shamans (the psychic) can entreat spirit allies and invoke various powers through the different entities they befriend (or enslave!); all are part of this group. Your Charisma modifier adds to your magical powers -either allowing additional channeling or bonus points.
I dunno. I think that's a solid system. The last group, just by virtue of having the combination of mechanical options, is a "more complex" class...but then, those classes are supposed to be more unique and rare individuals. Doesn't seem/sound "too" complex...to me. Doesn't seem like a "3e" style of confusion or option paralysis.
