Not sure it would have made a difference. I learned long division, but I've long forgotten how to do it. Or maybe I haven't. There wasn't a need to check whether I can still do it in over 30 years. But I probably forgot.

Looks like I was the opposite to you in regards to calculators. I always preferred to do it the hard way and only used calculators for boring things that I knew by heart, but would take me longer to do by hand and be error prone.

But I didn't pursue a career where this type of stuff was any useful and forgot many of the things I could do easily in school, like integral and differential calculus.

As the saying goes, use it or lose it. No matter how foundational, you'll eventually forget all about it if you do not use it anymore. There are even cases of people that completely forgot their first language.

I'm optimistic about AI because it can have more knowledge than any given human in storage. Eventually we all kinda specialize around something. Even the generalists among mathematicians have little insight into medicine, rocket science or astrophysics. So we all become the hammers of the saying "if you are a hammer, everything looks like a nail". But when including AI we get a broader perspective.