Playing complex strategy games for many years, one of the things that irks me the most is that hard AI levels often just give the dumb AI cheats to simulate it being smarter. To me, it's not very satisfying to go against cheating AI. Are any games today leveraging neural networks to supplant or augment hand-written decision tree based AI? Are any under development? I know AI can be resource intensive, but it seems that at least turn based games could employ it.
The challenge is that AI for a video game (even one fixed game) is very problem specific and there's no generalized approach/kit for developing AI for games. So while there's research showing AI can play games, it's involved lots of iteration and AI expertise. Thats obviously a large barrier for any video game and that doesn't even touch the compute requirements.
There's also the problem of making AI players fun. Too easy and they're boring, too hard and they're frustrating. Expert level AI can perform at expert level, which wouldn't be fun for the average player. Striking the right difficulty balance isn't easy or obvious.