I think the JSR did over reach itself. Hindsight is a wonderful thing but I think if the scope had been to just modularise Java itself and then have a separate JSR for a user space module system on top of that, it would have worked out better.
Yes, probably doing this incrementally (or at least as separately from "user land" as possible) would have been much better.
Though, this gives full program optimization via jlink, and probably modularizing rt.jar would have needed serious platform/syntax changes anyway.
What would you prefer instead?
An example is that the Module definition file (Module-info.java) is in Java source code. Despite the compile time benefits (performance, security etc) this brings, it really locks down how user level module systems need to interact with this. I personally would have gone for a straight XML/JSON/Manifest.MF/YAML/Whatever format which wasn't tied to the Java compiler so tightly.