> So while Java broke some big libraries/frameworks (not "pretty much everything though"), it can't really be blamed on them.
I think one of the reasons people use Java is to get access to those big libraries/frameworks.
I've worked at a few companies that used Java during the transition, so maybe I had access to about 10 Git repos that underwent this transition.
I think pretty much all of them required some tweaking e.g. adding extra dependencies in Maven when moving from Java 8 to Java 11. I actually became the "go to" person to do these transitions, having worked out what incantations were needed.
All of those repos, to this day, despite the effort that was put into them during the transition, now print out warnings about things being unsafe. The companies just ignore those warnings. I have 15 years of Java experience and I don't know what to do about them. My understanding is this is normal in the Java world now.
They are just normal web applications or REST services using databases like PostgreSQL, using e.g. Spring Boot, Tomcat, etc. Maybe those libraries do things they're not supposed to, I don't know. I have never used sun.misc.Unsafe in my code or anything like that.
Perhaps if I spent days studying the problem I could understand what was going on and what to do about it (although probably not, as the problems might have been in third-party dependencies.) But this wasn't money the companies I worked for wanted to spend. But anyway, my point is that spending days fixing stuff after an upgrade != backwards compatible.