Paul,
I think your anger is misplaced. Video codecs don’t grow on trees. Steinberg didn’t drop support, Apple did. If you want to get mad, blame Apple.
As for the notification - Apple discontinuing quicktime support has been all over the news.
I see no reason you can’t continue to use Cubase if you’re mid-project. Apple yanking support means that they will no longer be providing security updates. If you’re worried, disconnect from the internet, do your work, and move on.
-Tom