Some of the AI tasks could easily use such models. It would make the AI always pick the best options which may not be fun in an unbalanced game but technically speaking I don't see an issue for say choosing production, placing cities, policies, techs etc. Fighting and moving units is a way harder task but you could begin by at least make it learn through its own parameters instead of having it hardcoded.
The thing though is that if your AI is not capable of making an attack or puts city on the other side of the map I'm not sure you have the team to begin that kind of forefront work or just the opportunity to take the risk.
Of course the AI could be improved in many ways, but it's not just as simple
as wishing Firaxis would throw more money and effort at the problem now.
There are many simple fixes that Firaxis should do immediately, but there are
also many longer-term strategies that it would be foolish to attempt to
optimise now, given that there are more civs and enhancements planned.
The game in its current flawed state is enough to beat most casual players at
intermediate levels, and it gives most of them an enjoyable, challenging game.
Maybe Firaxis consider that that is good enough at this stage since the
initial release.
How do you decide on a set of "best options" in order to rank them in a
meaningful way? What might seem like a great option based on looking 2 moves
ahead could easily be a dreadful one when looking 3, or 30, or 300 moves ahead.
The specific example of China building Petra is interesting.
Yes, it is stupid to build Petra on the only tile capable of improvement.
But, by denying other Civs of that wonder, it might actually be a reasonable
long-term strategy, or it might also be awful in the long-term.
It is consistent with China's wonder-hungry trait. It can waste gold, time
or production that will later endanger the empire or send it broke. When they
get the right combination of wonders (or none!) to help themselves and hinder
other civs, the gamble could be enough for them to win.
It's not like there are no historical precedents for leaders spending money
and effort, or employing flawed strategies and tactics, on something that leads
to the ruin of their empires.