Like, you were a wizard 100 years ago, but then spells were super different and way less powerful, so now you get to relearn the newer better spells and casting techniques.

That's an interesting (and very Frieren-esque) bit of world building. But it does run contrary to the generic D&D settings/multi-verse, where the same set of spells have existed for centuries and across a multitude of worlds.

"When I was your age, you needed to know 9th level spells to cast fireball" is a cute crotchety one-liner. But it's not going to make any sense when you find a 2,000 year old spellbook with Fireball at the appropriate 3rd level slot. The DM would have to do a whole mess of retconning of an existing setting / pre-written material to make it work.

I imagine it’d be like learning to programming 50 years ago and then starting again now

As someone who did learn programming roughly 40 years ago, there are definitely differences. But an if-statement is still and if-statement and a function is still a function. The libraries and syntax can change, but the basic commands are still fundamentally the same.

I would note that modern programming-as-analog-to-magic would be more akin to everyone having a magic wand in their back pocket to do a set assortment of 3rd level spells per day which they don't even really need to think about other than the command word. Meanwhile, you've got this ancient elf flipping through a spellbook and spending an hour every morning re-memorizing a boutique list of spells nobody has thought to make a wand for in half a century.

Also a very interesting spin on a D&D-esque setting. But hugely divergent from printed materials.