Sometimes I get frustrated in the same way. Like right now, I'm playing a RTR campaign (mod) as Macedon and I have no problem with having many enemies and fighting on many fronts, but I'm basically fighting the whole world. It's still going well for me as I'm taking settlement after settlement, but I still would like some friends to come to my aid or something. The worst thing is when I'm fighting Rome and Carthage comes to their aid

You know it could be that while allies you absolutely cannot attack. You have to "cancel alliance" before doing any hostile movements at least one turn in advance. I think it would be a bit more fair.