Not everyone is doing Websites or Android apps.
PTC isn't using Hotspot, rather their own JVM implementation.
Just like C++, Java enjoys multiple implementations.
Just like C++, the best ones for embedded deployment with soft real time capabilities, are commercial, directly supported by hardware vendors.
D's biggest failure so far is not having a Google or Apple behind it, that would push the language no matter what naysayers have to say against the language.
Just like on iOS and Android, wanna play? Here are the allowed list of toys.