izigame.me

TLDR: very interesting but frustrating artificial requirements (i.e. can't end the struggle unless you're in specific phases, which change only after a very long time with no guarantee you'll get to the one you are aiming for).
The struggle mechanic was really interesting when I first read about it. The goal is to end it the 'struggle'. Ending it is supposedly about fixing the underlying problems (cultural and religious) causing strife within the Iberian peninsula. You're not supposed to just 'paint' the map, which is fair enough, we have enough of those already.
My problem with it is the artificial technicalities of the requirements. Let me explain.
Playing as Sancho of Castille, my long term goal is to end the struggle through 'Dominance'. This requires me to have every single county in my primary title be of the same faith and culture, and to be in the 'Hostility' phase (among other easier requirements).
I initially aimed to take over all my brothers' lands and enact the 'Unite the Spanish Thrones' decision. I succeeded but this dissolved all other kingdoms I had held at that point (Castille, Leon, Galicia, but also Navarra). This meant that I now have a dozen or so counties under my main kingdom being of a different culture! If you have a good steward (20+), conversion takes 8 years each. In the meantime, I played CK3 as normal and conquered most of the peninsula.
But the first hostility phase already came and went. See, the struggle has multiple phases and each 'involved' ruler has the ability to nudge it one way or another by triggering 'catalysts'. Changing phases takes a considerably long time, and if everyone in the peninsula is too peaceful, you might never even get into the hostility phase. To make sure we go into hostility phase again, I had to allow my vassals to war with each other to get enough hostility phase catalysts.
Everything was going according to plan. I was on track to converting all counties to my culture, only a couple left when we managed to get into the hostility phase. A few more years went by and now I just have one county left but the hostility phase is almost done (already at 850). It was okay, though, we were still on track. I had to wait only 2 years more to convert that last county.
But then at around 930 hostility phase progress, just about a year before the last county is converted, the stupid Waldensian heresy came about and some counties converted to that. The local rulers converted along with it. However, one of the catalysts that contribute to ending the hostility phase is to have involved rulers convert to the local religion. This gives +10 catalyst points each person converting, nudging us instantly to the next struggle phase!
I got so frustrated I immediately stopped playing. I can't save-scum as I was on ironman mode (I always play on ironman mode). I'm not sure I'll be able to play as a ruler in and around the peninsula again before these mechanics are tweaked so they're much less restrictive.