You never did math in high school
I think a certain amount of blame has to go to the teachers though as well.  My personal anecdote, I did extremely well in Calc AB in high school, aced the AP exam, aced first semester Calc III in college, then had a professor in linear algebra who, in hindsight many years later, was a terrible teacher. He zoomed through everything, didn't explain, and just <i>presented</i> rather than taught. I still remember his comment to help us understand - "if you're having trouble picturing 11 dimensions, picture a 3D picture, but in 11 dimensions." Thanks!  My last math course, Partial Diffs I did well again.  To a certain degree I feel "math is math" but how it's taught is different from prof to prof.