I disagree.
Similar to
@Gedemon , I have no formal programming education, but I modded NWN, and was able to greatly improve the ai (meaning, by subjective standards).
The ability to improve the ai does not rest solely in the capacity of the engine.
I think this is clear in the overall game design. There is a lot of tunnel vision in vi. Bluntly: vi's developers love the game, but are not very good at it, and they failed to consider options and outcomes because they could not see them, and did not account for the possibility that they might exist.
This extends into ai. The ability to improve it exists, but its possible they don't know how - logically and/or strategically.
To argue against this, you would have to explain away some incredibly obvious ai shortcomings.
But maybe they decided investing in ai wasn't worth it. Maybe the majority of players don't really care about having a challenging ai - they just want a pretty game with gadgets to play with.
This does, however, open up room for a competitor to the civ series, because the game has strayed far from what it was.