Flash was kinda dead anyway, not like iOS was the only reason it got phased out. Security issues and other technologies like HTML5 played a big role in its demise.
Apple can’t kill Unreal by blocking it on iOS, because Unreal is much bigger then just that one mobile platform, and it’s mostly a tool for high quality PC/Console games. And it’s currently becoming THE game engine out there, it might lose on mobile but UE developers are doing good job overall.