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