It's just too irritating to deal with diplomacy with multiple races. Figuring out what they will or won't trade, micromanaging the amount of credits or influence every trade, the interface just doesn't do what it needs to do.
I posted about this in the past, but never got a response. I was hoping it would show up in 1.1, but there aren't any changes there. I'm done playing GC2 for awhile, the diplo is a deal breaker for me

I'll check back at the next patch, you've got a good history of updating and fixing stuff.