It wasn't so much that it was Java (albeit ME without generics) it was more you didn't get an awful lot out the box.
You had to hand roll all your UI with drawing routines that scaled across various devices and handle all the touch/tracker button events yourself.
Networking was a minefield. Depending on your connection (bis/bes/tcp/WiFi) you'd have to pass various undocumented params. Think we had a modified version of some networking code a RIM employee has given us, God knows how you'd have figured it out as an indie dev.
The support and open source ecosystem wasn't really there at the time either. Just a couple of devs who were super prolific and knowledgeable on the dev forums (thanks Peter Strange, if you're about HN)