Well, PoEs seemed to be made precisely for me, addressing (if perhaps not fixing) every issue I had with Infinity Engine games. Still we talked about spell memorization system, not spell balancing.
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Spell slots and memorization are two different things. Sorcerers and Warlocks has spell slots BUT they don't require "memorization". Witch on pathfinder 1e prepare spells not with memorization but by using her familiar to channel and attune spells.
But i said that PoE 1 had extremely weaker spells and hence had to be changed to per encounter on Deadfire, because more powerful a spell is, more limited his usage should be. and some times, the spell comes with other restrictions. Eg, the strongest pyromancy(Forbidden Sun) having 1~3 uses per rest and taking 3 attenument slots, makes sense. If a regular fireball had the same limitation, nobody would even bother with pyromancy. Just like applying hard limitations on spells when the spells aren't strong, destroyed the wizard class on poe1...
PS : For me, PoE has a lot of dissociation between game mechanics and lore. Might affecting everything, including crossbows, firearms, magic, healing and etc is CLEARLY the most iconic example of game mechanics contradicting game lore.