Okay, first, resource gathering is actually the single most unrealistic element of most RTS games--I'm really glad Empire at War does it in the sensible, realistic way it does.
Second, people complained about the way the Death Star influenced politics in Rebellion. You blow up a planet, and instead of the rest of the galaxy cowering in fear that they'll be next, too awed to speak out much less join an outright rebellion, every planet in the whole galaxy would sign for the Rebels. While I'm disappointed to see politics disappear entirely from Empire at War, they come across as arbitrary and useless in most other games. I don't mind a game of pure military strategy.
As to the Rebels being weak--tactics. Outsmart the computer, dude.