Brad has been involved with the AI. He's not been much involved with the scripting. Likewise, I've been vocal in outlining issues with the scripting. I've no complaints about the AI. Brad has also struggled with the scripted bits (such as when he couldn't get the computer players to build the ships he wanted - this is presently heavily script dependent, and the general commentary from inside stardock seems to imply that they'd like that to change).
Remember, when players speak of 'AI', they're talking about a combination of wildly different modules that are created by multiple people with very different specialities. It is unlikely that, for instance, a C# AI coder would be involved in xml scripting to any extent, since coding AI in C# is difficult and requires years of practice, while xml scripting can be handled by a hastily-shaven chimpanzee with twenty minutes of on-the-job training.
This image may help:

Every red oval is a separate, largely independent module, which may have been implemented months before or after any other by programmers who may never have even met.
Now, I don't work for Stardock, and I'm sure this isn't 100% accurate (there's probably a few dozen examples on each side), but what you have is a large collection of semi-autonomous subroutines in the actual AI, and an equally large number of semi-autonomous scripts in the Scripts. So when players say 'the AI is bad', Stardock need to try and figure out from that which AI subroutine we're referring to, or which script, or even if we're talking about scripted behaviour or actual AI behaviour.
They're all basically independent; there's no over-arching 'AI' entity co-ordinating them. They take the resources they find at the beginning of the subroutine, and attempt to use them - so the diplo AI checks the scoreboard and diplo scripts to determine how it should act with another player; the tech picking AI refers to the technology scripts to decide which tech to go for, the ship designer AI looks at the blueprints and populates them with the best weapons of the types listed etc. Most of the AI's economic management is entirely handled by scripts.
The bit in the light blue on the right hand side is very good. The bit in yellow on the left hand side, where it is picking those initial conditions from, is where the problems largely lie. Brad, as a talented C coder with 20+ years of experience, works primarily on the blue stuff. Modders like myself, who have no access to the C, work on the yellow stuff.
If anyone from SD wants to chip in and contradict or correct any of this, do feel free, but this is largely my understanding of it.