For me I have two things to add.
1) For me it isn't really the constant battles, but I agree beating on the same Lord, 4 times in 20 minutes is boring. There should be a 3 month "healing" time when a lord is defeated before he's capable of going out to raise a new army. This would mean wars of attrition had more meaning. I remember one war where I had my 170 men, and I was smashing lords armies back to back to back. same lords 3-4 times and they slowly just ate away at my army because they just kept coming. There was no gravity to victory or defeat.
2) Unit costs per day as just too high. A good business in the game makes between 250-400 Denars per day. That's about 20-35 high tier troops assuming all your businesses are doing well and you dont lose them when you go to war with someone. Now my current army is 168. 2,184 denars per day to keep my army afloat. Since unlike other warband games i'm capped how many businesses I can run, I also need to caravans.. those are also capped.
Everyone at this point is like well duh, take fiefs. okay. I have 2 castles, and a city town. Because of constant wars, most of those villages are producing under 100 income. The castles about 200 and the town about 700. I have 2 caravans who do pay for themself and turn a profit, but I also have 3 other clan members as parties to defend my realm, all costing me money. They do randomly provide income surges with loot. I also have a merc army under me costing -400 day. (lets not mention the hundreds of troops in my fiefs to defend them) All of this is only netting me about -956 Denars a day. Yup that's a negative. So the loot sales for wars, keep my entire nation afloat if I want to use a strong military force.
That's trying to be a solo Kingdom and breaking out. Now when I joined a kingdom, I had additional income from the King. As a master of 6 villages, 2 castles and a Town. I should be making bookoo bucks. and in older versions I was. I feel like there was a tweak here and it's tipped too far south making the need large scale combat almost mandatory if you want to forge your own kingdom as I need that phat lewts.