I think that some of the reasons that Oraclewant to do modularisation their way are:
1. A custom JRE can be built with only the required JRE libs, to save significant of disk space, so the builder tool must somehow be told the application library dependencies to do this.
2. They want better security, reliability, and possibly speed than old frameworks like OSGi, which allows risky concurrent use of different versions of a library.
3. They want to do better JIT optimisations.
4. They may want to make better use of RAM for metadata.
5. They saw previous IBM contributed code in the JRE, and the IBM sponsored Eclipse IDE, and SWT, just saying...
However, if Oracle plans to stop allowing custom class loaders and does not provide replacement dynamic extension support, they deserve a revolt!