CK2 as game is never boring or somewhat. The way paradox develop the game is. Since the introduction of the achievements (a.k.a. my vitual penis is sooooo much longer) a playthrough got a half-life: That point when you've created and stabilisied your empire + one or two semi-powerfull king vassales. Usually after about 100 years irrespective of startdate and feudal tier you start with. Playing somehow geopolitical rational stretches the season to perhaps 200-250 years at best.
The problems (for me at least) are: Many balance desisons since mentioned achievement shenanigans. The "new" vassal rebelling system (RoI), the not properly adapted techsystem for the 2 new start dates, the imbalance between muslim and christian rulers (a muslim duke of aragon can put more troops in a war then the king of france, if you start at CM start and play up to 1066), fucking holy wars for free for everyone - for free!
The railroaded behavior of the AI and the inability of sayed AI to distinguish between the different charakters it's plays - only focused on to "killing" the player.
The list is much longer, but i'am to lazy to write the rest. Most people with my playtime of CK2 know what i mean.
Oh and bugs bugs, bugs, bugs, bugs and not to forget bugs.
I know my english sucks....