Blaming an Engine? I mean sure you could do that. You could Blame the Developer Crew as well. You could blame yourself (figuratively) the consumer. Its perspective but either way you have to look at all angles. You cant just go "Lack of or No A.I.". You have to question and look into it. Why is the A.I. so minimalistic outside of Main Story and Main Secondary Missions? City Life A.I. with cars and pedestrians is basic, yes. But thats seen on a few levels.
Youre looking at a game based on 50+ years into the future in LA, Cali. Very dense and trashed up city. Population is dense, but the people have become more dumb. Ever seen the movie Idiocracy? The civilians are very much like in that movie. Whether intended or by bad design, it fits. As society and technology grows, mans intelligence fades closer to the abyss. Not many games unless its a City Builder/Sims game where the A.I. is almost non-existent, has as much NPC's active all at once. Like you guys mentioned taking the A.I. of the creation engine and applying that to more than a dozen on screen NPC's, would but utter chaos and invoke crashes. Vanilla Skyrim (all editions) & Fallouts 3-76 cant handle more than 12-15 NPC's within the Players active cell/ugrid(5) range at a stable rate. They are intelligent to a point, but so few in comparison. Now imagine if All those NPC's in CP77 had that A.I.; youd probably be taking a straight bullet to the head every 2 minutes just trying to get out of your apartment in NC.
The issue would reside more towards Combat, though it wasnt bare bones.
Combat A.I. could use a tune up for sure. I beat the game (PC) about 35 minutes ago and the credits are still rolling. Got the Secret Ending. Anyways to the point. I played on Very Hard difficulty and I played 98% stealth and attempted to go the whole way without killing anyone, so that netted me nearly 200hours of play time with every single main & side mission. The enemies were easy for me to deal with, until the final mission where the difficulty truly showed. I had all of Johnny's gear, upgraded to full legendary and with max slots on each piece and his gun & car. I had a rough time. I would say the enemy A.I. at that point was on par with Deus Ex Human Revolution.