I've tried multiple times to reverse engineer our system with has ~10 schemas with ~200-500 tables each and a few hundred packages and procedures. It has never completed. Where do I go to see what is killing this? I'm assuming this product is built to scale to larger systems.
Size does matter.
You'll want to give SQL Developer more memory for the jvm.
Open your sqldeveloper.conf file and bump it up to say 2GB - larger models are quite resource intensive.
Do this with SQL Developer closed. Save the file, and re-start it, then try your RE.
Check response time of your server using ping - for local network it's 1-2 ms, if you get more it'll impact the import too.
If there are no references between schemas then you can import each schema in separate relational model.