I completely agree. It is hard though because I also want the world to feel dynamic and I do want certain factions to eventually gain the upper hand. I, eventually, want a kingdom to gain too much power so that it is a challenge that I meet the new kingdoms strength. A rapidly expanding kingdom looming over me creates drama and stress as I try to meet them in battle to stop their spread. But I want the ebb and flow to be relatively stable in that it takes a long time for any one kingdom to gain the upper hand. I also would like it to be harder for a kingdom to be eliminated so that they have a small chance to come back. I think peace negotiations getting more frequent and lasting longer would go a long way. Diplomacy and trade should become a way for kingdom's to negotiate peace if we want to roleplay as a (relatively) peaceful trader. Diplomacy should be a huge part of the game. But that is admittedly hard to implement without it being tedious.
I'd also love to see a dynamic where if the kingdom's armies are too far away for too long, more bandits appear and severely harm the regions income and prosperity (including food). Historically, war is a time for banditry and crime. If a kingdom spends all its time conquesting then I want the bandits to flourish and bankrupt the nobles. It could also result in a relation penalty since the nobles are not defending their villages and towns. Towns and villages could literally starve and stop producing money if things get extreme enough with lawlessness.
Overall, there is a lot of cool dynamics that can be added that makes the game take longer including kingdoms uniting against a rapidly expanding empire for self-preservation, nobles having a loyalty value to their liege, towns or villages rebelling if their needs are ignored, winter causing more army attrition which would slow campaigns and give kingdoms time for "house cleaning", diplomacy being as important as war, nobles getting disgruntled the longer a war goes on (putting pressure on calling for peace), peace leading to prosperity and feasts which boosts noble relations (making it have a purpose and be desirable), and even regions having loyalty (meaning that if it easier to take back your previously owned land and easier to defend it due to the populace being on your side). All in all, this game is amazing for early access and I hope we continue to get development! I am someone who wants this campaign to take as long as we want it to!
As a final thought, another option to give the player time to level up and get involved with politics would be to pause all battles for a year. If they introduce the dynamic where bandits get overly powerful and cause chaos during war, then perhaps a long war just took place resulting in just that. Banditry became rampant which is what lead to the main characters family being killed. The kingdom's might call for a year of peace to combat the bandits. This would give lots of opportunities for the player to take out small looting groups, get a massive relation bonus from other nobles when you killed bandit hide-outs, and give the player time to become an impacting force in the world. It would also make sense with the story.