The JVM has a selection of four generational GCs. Two of them are the most sophisticated GCs available anywhere.

It's not a matter of some unique brilliance. Java is simply in such high demand that it has the sufficient resources to have state of the art optimising compilers and GCs.

Hm? G1 is a generational GC? And so is Serial/Parallel. And work on generational ZGC is ongoing [1]. Not sure what you're referring to here.

[1]: https://openjdk.org/jeps/439