I've yet to see a real world use that is meaningful. Mostly it just adds deployment bureaucracy for opting in to stuff that used to be there by default. I'm not seeing a huge adoption of modules outside of Java's core libraries.

A good thing that came out of it was that it forced them to untangle the 2 decades old standard library. This was disruptive but it seems to have also unblocked a bit of progress and also allows the to have experimental modules in non lts releases (9,10,12,13).