Thankfully there are projects out there to preserve some of the content and I guess use the stand-alone player, like Flashpoint (https://bluemaxima.org/flashpoint/). All of the open source implementations I knew about, including Mozilla's basic js version that was intended for Firefox, seem to have been abandoned AFAIK.

On the upside, HTML 5 opened up cross platform support for a similar feature set albeit via a different language and API. Canvas and WebGL support in a browser opens up fast more platforms and devices to bring able to provide games or animations compared to a closed source blob. Integration in the browser should also prevent it being as exploitable as the updates are pushed via one component, the browser, rather than requiring browser and add-on updates. On the other hand, Chrome basically becoming the new IE6 in terms of market share and being at the heart of other browsers liked Edge has created a dream multi platform, multi browser attack/exploit target.