One of my favorite things about putting together Flash movies was the interactive menus. Sure, preloading was a chore, but the reward - in my opinion - was being greeted with a fun and unique menu. Usually they were on collabs with lots of parts, special credits or even minigames, bonus featurettes or easter eggs to amuse yourself with.
A lot of the old flash cartoons I have uploaded here obviously have had their menus and other things cut when they were converted to video, including the features that came with them. Something that made them special that had to go with the inevitable death of flash player for the web.
I've noticed that a lot of that interactivity in general is removed from video players, like the death of annotations and community subtitles on Youtube. One i'll always remember in particular was CAD: The Annotated Series, in which anyone on Youtube could contribute annotations overlayed on top of the CAD animated series, which was the only way to really tolerate watching such trash. Fortunately, it was preserved here before Youtube killed off annotations for good.
Anyway, maybe someday they will come back as menus continue to live on even in the slow death of physical media where they were ever present on DVD's and Blurays, as you sometimes still get cool menus on streaming VODs. They have a charm to them that I will definitely miss. Maybe they will live on in some fashion through Ruffle? I haven't seen it in action yet, but here's hoping.