He's right
Former Gentoo Java lead here. I totally feel his pain as I burned out some years ago. It's even worse when you're trying to allow users to build the stuff from source. I'm familiar with many languages, including those that are known to be particularly troublesome for distros (like Rust and Ruby) but trust me, Java is the worst of all worlds.
One reason for this is its approach to optional dependencies. Take log4j 2, for instance. When I last looked, it had about two mandatory dependencies but tens of optional ones, most of which hardly anyone would care about. That's fine if you're grabbing the precompiled jars with Maven or Gradle or whatever. Grab just the ones you need. Or hey, just grab them all, it's only a few more KB to download. If you need to build from source though, as Fedora policy dictates, you're screwed. Although it's possible, no one uses a preprocessor with Java so all those dependencies that are optional at runtime suddenly become mandatory at build time. And guess what, those dependencies have more dependencies and so on and so on, and before you know it, you've had to package and build half the Internet. Maintaining a single distro package, particularly in Gentoo, carries significant overhead that just doesn't scale in the context of the Java ecosystem.
Gentoo is not as strict about building from source as Fedora is so I considered just using precompiled jars where possible. You then have to ask what the point of packaging Java stuff is at all though. There are some small benefits but I didn't feel it was worth my time so I moved onto other things. I'm now the Gentoo Games lead. That's much more fun!
