Yes, Flash was a great tool to create stuff. (I only used it in Macromedia times)
This however also lead to an abuse and for a while you had websites, fully in flash which broke so many things (deep linking/bookamrks, browser history, etc.) combined with unintuitive navigation and slowness due to animations ... plain overuse of an otherwise good technology.
Modern JavaScript frameworks have support for this and a result of Flash's experience is that browsers have specific APIs for that ... however: each new generation of developers has to learn :)
Speaking of Flash and alternatives to CSS there was a whole UI language built to run in the Flash player called Flex which had an amazing layout engine. You could - in code - define your own layouts which could then be used on any components. I've been wishing someone would port this to javascript for years. Imagine if developers could have just created FlexBox when it was needed fifteen years ago instead of waiting on W3C.
And the standard libraries, cross-platform support, and industry-trailing IDE. They didn't even have a stable debugger for years but that didn't stop them from charging $800/seat to see if they'd fixed any of the problems.
I wish everyone in web developemnt stopped only looking at the thing that makes it easier for themselves and start to focus on what's best for the users.
True, although if Flash had stuck around long enough (i.e. if iPhone hadn't signed it's death warrant) I'm sure eventually we could have come up with a solution for a11y.
Most of the flash sites that I really remember consuming were actually very simple documents that relied on flash for presentation, so it would be easy to provide a screen reader friendly version of the content.
Also a lot of flash content was cartoons and games which don't lend themselves to screen readers anyway.
It was the player that wasn’t great.