Open standards did not beat Flash. A bigger proprietary platform bully sent Flash to it's doom - Apple's iOS. Adobe's Flash was vulnerable because it had to seek Apple's blessing to be part of Apple's platform, and they were spurned.
This is the lesson of being a sharecropper - even a massive proprietary-source company, Adobe, are powerless when the platform owner enforces it's control. https://www.tbray.org/ongoing/When/200x/2003/07/12/WebsThePl...
Yes, open standards win in the long run, after Apple have profited significantly from the closed approach they are taking now. At which point it's a meaningless victory.
The point of the article is, be aware you are just a sharecropper, and working on Apple's lands for as long as it's in Apple's interest. And Apple owes you nothing for all your hard efforts, it will change the environment for it's own corporate interests. And you, the developer, are mere insignificant collateral damage. Remember that Steve Jobs killed Flash. And there was nothing Adobe could do to avoid or mitigate it.
Current iOS developers have already accepted this, willingly or unknowingly. It's the new folk who are attracted by the new shiny thing, need to be aware of the consequences of working on an Apple controlled platform.