Crusader Kings II hasn't been updated since 2021, and it's fair to say that it's been put out to pasture in favour of the sequel at this point. Mods like CleanSlate have accumulated a substantial amount of fixes for bugs and inefficient scripting which haven't made their way into the official release and likely never will, but the rules say you have to choose between taking advantage of those bugfixes and earning achievements. (CleanSlate doesn't even include fixes for historical inaccuracies—CK3 got an update to address the fact Murchad mac Donnchada should never have been listed as king of Munster, to give one example of many, but CK2 is still incorrect despite it being much simpler to fix since he's not tied to a tutorial.) A patch to let people gain achievements while playing an overhaul mod like CK2Plus, HIP or Tianxia would be very appreciated, since the incentive to play pure vanilla CK2 diminishes the shorter the list of things it offers that CK3 doesn't becomes.