Yes, the tactical AI in Civ6 was alright, certainly by the end of development. Even Civ5's AI, which I think overall performs worse, was tactically better than it seemed.
I've said many times the Civ6 AI underperforms in combat, by a lot, compared to its capabilities. The main problem with the AI's combat performance is actually getting the units there. It has difficulty navigating the traffic jams, it ends up with some assigned units not making it to the target area, it fails to move them in a manner that reacts to battlefield changes, etc. It's not even something the AI engineers should be blamed for because pathfinding is hard and the mechanical design of Civ5/6 is very unfriendly to the AI. The game's maps have 1UPT while being small, units have low movement range and the already small maps are further constrained by water, mountains, small distances between cities and then neutrals like city-states. It's hard.
I found the encounters where things work out just right for the AI to be memorable - if it manages to get a decent force to the front lines, it performs pretty well. Not perfectly - the Civ6 AI is IMO too reluctant to focus down individual units - but it's a good performance. But most of the time it loses the battle before even getting there. For that reason I'm very happy about the Civ7 commanders, it sounds like a change made directly in response to traffic jams Civ5 and 6 suffer from so much, which can help the AI and reduce player annoyance at the same time.
