People do things in real life without needing to map video game mechanics to them, I see no reason why it should be different for in-universe rpg characters. You trying to strawman my argument increasingly makes it look like you cannot accept a story with any less 4th wall-breaking than Order of the Stick.
Tell me you've never known a competitive runner, weight lifter, cyclist, fencer, swimmer without telling me you've never known those people.
They have logs, regimen, strategies and such following a pattern that goes well back to the middle ages.
Heck, tell me you've never read historical texts purporting to be manuals for sorcery. I have maybe a half dozen english translations of 16th century books claiming to be 8th century books with weeks-long processes for summoning spirits, enchanting rings, making magic mirrors, hands of glory, etc. You have to track moon signs, which plants flower or bloom on which day, what the breeding season is for different animals, on and on and on. Yes, its that complex because its mumbo-jumbo and the complexity hides the mumbo behind the jumbo.
And it's not like the plateaus between spells are invisible.
"Hmmm,
fireball takes 3x as long to prepare as
magic missile but I can only cast it once, unless I cast a 5-dart
magic missile when I can't cast
fireball at all until I rest. And if I cast 4-dart
magic missile I can't cast
shatter and shatter takes 2x as long to prepare as
magic missile, but casting 3-dart
magic missile has no impact on how often I can cast
shatter or
fireball. And you know, it costs 50gp to transcribe
magic missile, 100gp to copy
shatter and 150gp to copy
fireball. There seems to be a natural break point between these things that correlates cost & difficulty to transcribe, preparation time, and capacity for daily spellcasting.
I shall call them Laurentis Levels!" - the Wizard Laurentis, 7 hojillion years ago