Not to mention that in later editions, you could easily create scrolls or perform rituals of obsure use magic. You got scribe scroll at level 1 as a wizard and everyone got a feat at level 1 in 3e.The biggest issue though is simply the sheer number of spells casters get in later era D&D. Remember, your 3e wizard (or later) is getting bonus spells at each spell level (probably up to 4th in 3e) and can recover spells during the day without resting. Plus, since 5e makes all casters basically sorcerers, you don't need to lock in slots. You can have fireball and Leo's Hut, and if you don't need the Hut, you can just fireball again. Plus, with upcasting, you can simply burn that 3rd level slot on a 2nd or 1st level spell in a pinch.
It was far more common in AD&D for casters to have unspent spells all the time. And the opportunity cost of taking spells that were more limited use just wasn't worth it.
OTOH, in 5e, I am seeing spells being used that I had never seen used in D&D before. Heck, our Cleric just cast Control Water and the group was nowhere near a boat. I'd never seen that before.
It's really like comic book multiverses. All the same people exist in each edition. However Elf Wizard A, Elf Wizard B, Elf Wizard 250, Elf Wizard 336, Elf Wizard 400, and Elf Wizard 58 have origins, limits, alignments, history, and capacity. Elf Wizard 58 HAS A BEARD!