Where I worked, we had a designer/cartoonist, and me.
All I had to do was to pick his images and find a way (ActionScript) to make them animate and react according to user interaction. Sometimes, it wasn't just a banner, it was a small simple mini game for advertsing or more complex, educational game, for example. I really hated Flash and the need of a script for it, preferring to do animated GIF banners.
I am not a fan of jQuery either, I prefer vanilla JavaScript, and I prefer to do very little JS, because I see them as a resource hog and unecessary in most cases. I am happy that Bootstrap is ditching jQuery to use vanilla JS, but there are cases where JS isn't even needed. I can give a few examples that can show how great HTML5 is.
Last week I had to do a modal, and load it in a situation where I couldn't load a JS together (don't ask me why, the LMS I was using simply couldn't let me do that) so I used some "black magic CSS" to load the modal which works for all browsers, even the old ones - the checkbox hack. I could've used the ":target" hack too, but that would require a little JS to make the browser history ignore it. Anyway, my trick works flawlessly and does not need JS. Although the checkbox hack isn't very clean or does not follow any standard, it works well for the purpose and works exactly like a JS solution I could have done. And it was a quicker solution.
Back to the Flash, HTML5's canvas can do the same job if not better, it just has to be well programmed, and to do that, just make it as simple as it can be. I'd say to use Flash as a fallback if you really wanted to cater for the older browsers, but frankly, don't. Especially in a moment where Flash is being killed for good this year. I had 2 good news this year so far - The death of IE11 and now Flash...
"Design isn't just what it looks like and feels like. Design is how it works."
JOBS, Steve.
READ: Right to Repair sucks and is illegal!