Hi there,
Let me explain. In the beginning you get simple factories, labs etc. If you happen to capture a planet in the later game that has few/no factories then all that are available are the uber-structures, which take about 300 turns to build. So such planets are essentially useless ...
It would be great if there was an Obsolete section in the structures list that you can expand and then build smaller factories etc in order to get enough production to tackle the big boys.
Please let me know if this is already in the game
Dano