Aside from missing functionality, there are a few bugs I noticed.

1) a major race's homeworld isn't marked to belong to that race
2) minor races join other empires without having even come in contact with them.
3) several worlds on the map are revealed over time, without exploration. These worlds do not belong to any empire you might come in contact with, so they're not revealed through diplomacy.

I'm sure you know about these bugs already, but just thought you might like some feedback.

1) That is right. Because the other majors have no food building and they don't build foodbuildings -> famine -> rebellion -> system lost.

2 and 3) That is a feature of the Alpha Version. The AI-majors know some minors at the beginning of the game, so they get diplomacy relations (maybe membership) without flying to their systems.