Definitely more the language ecosystem than Java itself - coding in Java itself is painful to me as well. I actually write most of my code in Groovy, some in Kotlin and Scala. But these things keep me liking the JVM -
- maturity of the infrastructure (monitoring, debugging, IDEs, build tooling). I love that I can fire up my debugger and remote attach to a process running on some other host and set a breakpoint for a specific condition to catch a bug. Or that I can do the same to profile memory etc., all with very mature tools.
- very good performance - smack bang inbetween C/C++ and higher level languages (acknowledging that startup time is a big hole in that - but not an important one for me)
- truly cross platform - none of this python style, cross platform except half your packages are really written in C and won't compile unless an entire ecosystem of dependencies is there to support them, and even then some of the flat out don't work on some platforms. This extends deeper than most other languages ie: you can get closer to low level OS features while maintaining 100% cross platform capability.
- strong / static typing under the hood which you can access optionally (eg: languages like Groovy / Kotlin let you write high level code without being burdened too much by the overhead of static typing), but all the Java APIs, ecosystem of libraries are all statically typed so you have good guarantees and excellent documentation.
- deployment behavior - I can run the JVM, give it specified memory footprint and know it's going to stay within that
