Well, since you're so interested... here you go. Playing against the AI involves using well-honed combinations and skills. This minimizes unpleasant experiences such as losing troops, Castles, etc. Consequently, there are more positive emotions from the gameplay. What will I do when playing against a human? It's obvious that my favorite tricks and tactics will either not work at all or will work poorly. Will this make me happy? Of course not. In fact, I get an infinite number of possible combinations that I need to find in order to win. Is this interesting? For some, yes, it is. For me, it's not. There will be many defeats and disappointments with this approach, especially at first. I have very specific emotions and feelings associated with this game. Why would I want to spoil them? Games should bring positive emotions, not negative ones. If playing against the AI brings these emotions, then it is fulfilling its purpose.
Next. Various little things. Let's say we start a game, and I don't like the starting artifact. Usually, I click on Restart Scenario in such cases. But in a multiplayer game, I won't be allowed to be so picky, right? However, even all these artifacts fade in comparison to the endless restarts to get the desired hero in the tavern. To clarify: the desired hero is the one that brings +350 gold daily. Because I don't see the point in keeping a hero in the Castle who won't bring any benefit. Instead, I always have one hero traveling and winning, while the other visits external creature dwellings, mills, and other useful places. At the same time, this same hero also generates income. Ideally, it would be good for him to also master the "Estates" skill, so that the income from him is even greater, but that depends on luck.
Next. Time. I think the very idea of sitting and waiting for another person to take their turn is absurd. I am willing to wait N seconds for the AI to take its turn. But a real person will definitely take more time for their actions. What should I do during this time? Stare at the ceiling? Read a book? Watch a movie? That's silly... And if there are not one, but four live opponents? Or even more? I'll hang myself... Unfortunately, I don't have that much free time to allow myself to wait for someone. When I play against the AI, I use the maximum amount of time for pleasant (personally pleasant) activities. Note that, despite all this, I absolutely do not want to limit myself in time. I can spend ten minutes on one game day to calculate who should go where, what artifacts to exchange, etc. Would you agree to such an opponent in a multiplayer game? :)
Next. That very realism. The heroes' movement speed is minimal. The troops' animation speed is average. There is no fast battle. Choosing a random Castle comes down not to choosing a preferred Castle, but to choosing the Castle that best fits the surrounding landscape and nearby objects. Guess which Castle the player who starts on a swamp will have? And I don't care that this Castle might not suit him. I'm used to it, and that's it.
I think I'll end my post here. I could recall all sorts of little things, but why? The main thing is that you have probably already understood my main idea: maximum enjoyment per minute of gameplay. Everything in the game will be subordinate to this rule. My interests are the most important thing to me, which, as I think, automatically makes multiplayer games, even in alliance with people, unacceptable for me. Not to mention fighting against them... And in general, I'm a pacifist. :D