“It’s probably Matt Mercer’s fault.”
Combining ideas from several different threads, I'm imagining a world (that will never occur, at least not under WotC's watch) in which:
- Rangers don't have normal spell slots. Instead they have something like Warlock Invocations, in which they get to pick and choose their favorite toys, some of which may involve spells.
- Paladins don't have spells at all. Instead they are designed like Battlemasters or Sorcerers, in which they have a resource they can spend on Smites. They get to pick from a list of Smites, getting more choices at higher levels, and swapping them out whenever they gain a level. They still get Lay on Hands, Auras, Channel Div, Fighting Style, Divine Sense, Faithful Steed, etc.
- Druids become half-casters, but their Shape-shifting becomes more powerful, plus some innate nature-y magic (like talking to animals, etc.)
- Sorcerers don't have spell slots. Instead they use the Five Torches Deep mechanic. (Briefly: no limit to spells cast per day, but every time you cast you make an Arcana check, and on a failure you can't cast that level spell until a long rest. Also, bad stuff can happen on a failure.)
- Bards become half-casters, also with an Invocation-like mechanic.