I believe it’s possible with decision trees and forests, even though they’re very complex inside, to calculate the contribution that each independent variable made to the final result. Of course, I suppose those haven’t been deemed “AI” for a few years.
Sure, you can step through it and see what's occurring, but there's zero explanation to accompany it. To fully reverse engineer and explain a reasonably complex AI model would be quite the undertaking. Instead, we have prompt engineering. It's easier to figure out how to ask the black box nicely/properly to do what you want than to open it up and optimize/tune it proper. If we assume that we get that far, I fully expect the resulting explanation of the black box internals wouldn't be considered a reasonable/reliable basis for making medical decisions.