I'm not sure what your real world experience with Java is, but GC is actually quite good and in server side Java I had no issues for years. G1 evolves and I had no issues with it. In Java 12 there is ZGC that have similar goals as Shenandoah, too. It is not like Shenandoah is something that is intended to be mainstream in Java. While G1 is optimized for throughput, Shenandoah is sacrificing performance for very short stop-the-world phase. It really depends on your requirement which one is better. There were multiple GCs before and alternative vendors have their own, for sure. What is your current pick and why is it so much better?

JVM is really good tech, it allows ecosystems like Scala, Kotlin, Clojure etc to exist. Since Java 8 there is class data sharing that may reduce your startup time and memory requirements a lot, especialy if you run multiple instances with same classes on same server.

Java ahead of time compilation was experimental since Java 9 and GraalVM should also help a lot if startup time is critical.