> I still can open my decade-old Java projects, run build with modern Maven/JDK and get working code - in a few minutes.
Try any old Spring project, where anything newer than JDK 8 will be incompatible. The only saving grace is that JDK 8 is still available, but even it will eventually reach EOL. And then you look at JDK 11 projects and realize that they won't run on anything newer due to Lombok issues, so that's another thing to update and fix.
I think the experience of code rot is universal and increases with the amount of dependencies you have.