My personal opinion:
1. Flash MX 2004 -- Wasn't fun to use
2. Flash 8 Pro -- Decent if you still live in 2008
3. Flash CS3 -- not fun to use
4. Flash CS5.5 Pro -- It's pretty damn good! Same as Flash CS6
5. Flash CS6 Pro -- It's good but laggy and no dark mode
6. Flash CC 2013(?) -- Awful, lag and unusable
7. Animate CC 2015 -- Timeline controls didnt work so not the best but good with patcher
8. Animate CC 2019 -- Almost as good as 2021 but kind of slow, wasn't as nice as 2021
9. Animate CC 2021 -- The best by far: good UI with scaling, improved icons, more features, etc