The combat system in Humankind is definitely its best feature. Unfortunately the AI has no clue how to do it. I think it should be a lot of fun in multiplayer.
Surprisingly the AI is actually pretty good with move, shoot, move units like what the huns have. I was mostly able to come out ahead in all the battles because I always kept reinforcements nearby. In a straight fight it would have decimated me despite army for army our power being similar. The AI perfectly understands zone of control, what positions give it combat bonuses, and line of sight. What it doesn't understand is how to position itself in a way that it's still safe after it gets its attack in, and the huns unique unit and units like it bail it out there. I mentioned the two front war to say I didn't roll an easy map. I got ganged up on in an era where you're still weaker than AIs. The game is just actually easy enough that a ~monarch player in Civ IV can probably comfortably win on the highest difficulty. Even without using some of the more broken strategies in the game.
The problem is less the combat AI, though it is less impressive when you move it away from cultures that can attack and retreat in the same turn, but more in the economy side. The economic play is a joke. Production is king and it's not even close. Food is effectively useless after you pass the very low bar of having enough to tech through the ancient era, gold is a bad version of production, and science needs are minimal until you decide to end the game and turn all your production into science directly with no loss of efficiency.
In general it's also just a balance nightmare. It's hard to point at something in the game that isn't broken. The pre civilization era especially is broken because staying in it a bit longer gives you free reign to terrorize two+ AIs and steal at least one if not two cities for free.
And while I haven't tried, from what I've heard multiplayer is pretty lame. Huns are 100% ban rate at this point because they're just busted in the hands of a human that knows how to do a timing push, but more relevantly the game has minimum combat damage and "indirect fire" is a rare ability for a ranged unit to have. Archers do have indirect fire, so combat for the entire game is "rotate meatshields to protect the archers who do the killing". That's the level 0 strategy anyway. Some unique units are really good and are worth using over archers in their era (like the ridiculously overpowered hun horde as an example), but the archers are always an option and end up being better than what you may want to do a lot of the time.
For people who haven't played, Hittites into Huns is the strongest military civ you can possibly have in the Classical era. Hittites give a combat bonus throughout the entire game when you pick them, and the Huns have a downright stupid unique unit. I don't even know what to compare it to in Civ IV. Maybe like...Keshiks at half cost, unlocked at the start of the era, +100% damage bonus vs spearmen+pikes, the ability to make 3 other versions of themselves after pillaging a tile improvement, and the ability to make another copy of themselves after winning a battle. Not an exaggeration. Thankfully the AI doesn't abuse the sheer speed the Huns can make a massive army of them and just uses them like a normal unit, but that doesn't change that they're the scariest unit of the era in a straight up fight.
Edit: Oh, I forgot my two biggest gripes two.
1. The entire game just feels like a bunch of the devs sit in front of a blackboard listing out ideas that they thought would be cool and put them in the game without considering how they actually interact with other systems. There are a lot of examples of this, but I'll go with simultaneous turns which leads me to:
2. You will basically never get the attacker advantage vs the AI because turns are simultaneous, the AI waits for you to move before it moves if you could attack them, and good luck beating the computer at inputting an input.
Edit 2: I also forgot by far the stupidest mechanic in the game. You can have infinitely negative money and influence. It doesn't matter beyond you not being able to buy stuff. You can even still use money to get yourself out of a war despite you having literally none. Negative 2 million is the exact same as -10 which is the exact same as +20 which is the exact same as +40k (at least in the lategame where 40k doesn't buy anything).