I've always been quite proud of my ability to acquire at least a moderate mastery of most software (I can use both vi and emacs!), but I never managed this with AfterEffects. I don't know what it was, but I always seemed to end up in some interminable state that I could never get back out of without quitting the whole damn thing, or I could never make the timeline behave itself (I never had this problem with Flash), or... it was just endless misery for me.

I very much admire people who are adept with it, and sometimes when I watch the opening sequences in films, or certain types of adverts on television, I can even imagine how they might have achieved it with AE - but for me it was a great relief when I never had to use the damn thing again.

(I spent about a year maintaining a proprietary ActionScript library that would render AfterEffects animations - not dissimilar to Lottie, in fact, except almost certainly a whole lot worse, especially the bits I wrote given that there are probably some horses who understand AE better than I did.)