It was extremely to do a UI application with Flexbuilder, very similar to using VisualBasic 6.0. Just drag some widget and connect the event to some functions. Also drawing and animating vector graphic with the Flash authoring tool was extremely easy.
Today there is still no software that is this easy to use. You dont see 7 years old kid coding vector gfx animation with javascript and css :)
But back in the day it was not uncommon to see complex flash animation designed by 7 years old kid.
Sad that the best they can do is Swift Playgrounds for iPad; creating what is essentially a JSFiddle/Codepen for apps that can't be deployed without first paying their $99 dev fee toll.
In that spirit, I use Tumult Hype, which truly is Flash, and can be acquired without a pesky subscription.
But an app with vector animations should have been doable (not to hard in theory) if you could have found the investment for it, right?
(Unity do have animations tools for artists (it is partly made for artists) but not so good for vector graphics and not close to flash, and definitely not back then.)