Meanwhile, it was (as you say) years ahead of standards and the most ubiquitous non-standard standard on the web. In early years it let web designers expirement. Most of those expirements went badly, but many ulitmately preceded and shaped the web of the "future."
Animated interactive UIs, video, audio, rounded corners.... These appeared as flash first and challenged html+ to keep up (with the better parts).
We've all been talking s--t about flash for years. But ultimately it was in use because it was useful and the web may have turned out worse without it.
On tools, this is inevitable. Tools don't last forever and professional these days need to retool periodically. As flash exits left, there is room for new entrants into the 'tools for ex-flash designers' segment.