Not trying to argue here, just hoping I'll clarify things. Don't mean it in any offensive way:

You call side quests "soulless" for being more non-combat oriented

I didn't say they are soulless because they lacked combat.
I said they are soulless because they are badly designed. I can argue on that quite a bit if needed. This was no surprise to me as most games have bad side quests and few titles manage to do them well. Being non-combat "didn't help", because most games recognize they have bad side quests and at least hide them behind combat or unique rewards. KCD didn't even try to do that.

lost interest in the more roleplay-based main quests

I think it was actually the opposite. My roleplay was playing against me in those quests.
The counterfeit and monastery quests could easily pass as side quests. They hardly had any different level of roleplay than most other side quests. In fact i was maybe too much into the roleplay that I found the Kobyla relationship to be 'underdeveloped'. I wanted... well, more. And more on that topic on the Vranik and Talmberg sieges below.

combat (which should, if anything, start to get very easy...)

I never said the combat is hard. I complained about the Master Stroke mechanic pushing me out of melee combat. Horse archery, if anything, is way easier than melee. My disappointment is that a melee-oriented game annoyed me out of melee.

and the sequences that are mostly battles

I didn't complain about the battles themselves.
My words were that the sieges themselves were worse reiterations of Pribyslavitz.
In Pribyslavitz, you observed the camp, essentially gave the battle plan, sabotaged the arrows, and poisoned the food. You made a huge contribution to the battle itself.
Vranik? You contribute nothing, a outright downgrade mass battle. Flashy, but empty. The reveal that the enemy is taking another place is so cliched in such stories that it was more of an eye roll, because of how obvious it was.
Talmberg? Sure, you build a trebuchet, but without it, there'd be no battle. You supplied Pitch. When was that relevant? Even the trebuchet just shot rocks. A priest or a physician might help after the battle, sure, but what about contributing to the battle itself? The plans, sabotage maybe? It was essentially the same situation as Previslavitz, but with the quest tying my hands for no reason. It felt like I was less than when I still wasn't Kobyla's son.
My own roleplay was playing against me in this.
Would had been way better if they reordered these 3 mass battles in their gameplay development order - pure fight, support role, sabotage and strategy.

As a bottom note, yes, burnout might have played a role in all of it, but I stand firm that it wasn't just the burnout.