Speaking from my own experience, AI is still not great but that's more or less how the AI works in every other wargame/strategy game. HoI4's AI is far worse, for example. At least if you ask me.
As for JTS titles' AI, it's still not very impressive although I wouldn't call it "brain dead". To give an example, I had a tough time the other day trying to break out of Falaise pocket against the AI, playing as the Germans. Any AI that forces you to rethink your strategy is a passable one, in my opinion.