In my experience, having worked closely with these technologies in my day job during this era, the average person talking about it has an oversimplified view of the technologies and comes to the wrong conclusions.
Adobe did not want Flash to die, and their product manager was very involved in the community to figure out what needed to happen to prevent that. I don't think Adobe invested enough into those demands, but still there was steady investment made. If they had more time, and Apple wasn't such a bully, the tech could have evolved and survived.
Adobe built Stage3D so that one API could target GPUs across desktop and mobile. Think WebGL, which was released around the same time. But production-ready due to the distribution advantage the flash player had over browsers at the time.
Adobe funded open source projects such as Starling to create scenegraph-like APIs on top of Stage3D, providing an on-ramp for all existing AS3 devs to the new paradigm with their existing API knowledge and tool chain.
At this point in the timeline, any AS3 dev could write cross platform games and apps if they picked up a handful of mobile GPU concepts like draw calls, texture maps, and bitmap fonts. (You could take all these things for granted in the traditional Flash scenegraph.) Unity existed at this point but did not yet have dedicated 2D libraries. You'd be rendering your 2D game onto a face in a 3D world, with a fixed camera. Total overkill. They wouldn't be as performant as Stage3D for a couple years.
I disagree with the assessment that Adobe was a bad steward because I saw them trying with my own eyes.
I also disagree that Flash couldn't do native apps with native performance because I built them with my own fingers.
Lastly I disagree that web standards obsoleted Flash because where are the web games? Why aren't they playable on mobile safari? Why don't the web standards come with a dev environment and where are the dominant Flash monetization models?
Apple played hardball so that the only way to be on their platform was to use their tech in their way signed off on by their reviewers and monetized by their app store. They also wrote FUD pieces like the famous Jobs letter.
Who was the villain here? Is Apple justified robbing us of a Maker's renaissance era because it wasn't mobile ready at the literal dawn of mobile computing?