Same for 1.59 the game pays too much empahsis on raids and that the other kingdome "think they" can capture atleast 1 holding of yours.
While even the garrisons in your weakest castle + the milita will defend itself vs what they can muster.
Imo the formula need to add in how many of their lords is in prison(tbh this should perhaps be an auto-trigger for peace, where they pay you tribute or nothing at the very least).
Those defeated lords will act like pestlords until about 1000-2000 days ingame, thats when they start to defect by themselves(as they run out of money from what I gathered by my playing, and some info from the devs about the lack of defections)(you can however start recruiting them much earlier if you got the denars to do so though).
But yah atm the formula for desiring peace is way to low, there is barley any peace in those 1000+ games I've played.
Typically the only time you get peace with a faction, is when another declares war, and if your faction thinks its strong enough it will be at war with 2-3 and still have 0% intrest in peace, even if they are loosing castle after castle, then recapturing it into infinitum - this Hawaii-wave of war isnt "fun imo" need to turn up the desire for peace abit more, loss of life should have much higher impact on the kingdomes, as in when you recruit soldiers the same amount of ppl should be depleted from prosperity soon enough there wouldnt be enough ppl to recruit).
(I havent played with mods, but they take into much more advanced stuff like this).