What do you guys want? an always successful crusades? Impregnable catholics? Precise history?
The first crusade was successful ONLY because muslims were in a political crysis (civil war).
The muslim conquest of Spain was successful ONLY because Jimena was in a similar crysis.
The Sejluks subjigated the romans only because a constant crysis in the empire.
Once those states consolidated - Kingdom of Jerusalem fell and Reconquista happened.
Later crusades were not as successful. Just because they were called at a wrong moment.
In this game it is modelled correctly. It is not geography, that defines the conquests, but it is political situation.
Instead of Iberia muslims can get Italy or Greece. Instead of falling apart - empire can become the Rome Reborn. It is up to you, as a player, to help your close and far away AI to achieve their goals.
If you want Fatimids to be less successful in general - try supporting their victims(in every way possible), instead of building 20th century centralized Ireland before 1100.
I want realism and satisfactory game. In reality it wouldn't be enough to make superpower from Byzantium after 1066. Here it's enough if my new ruler is better- no crisis, no consequences of previous ruler weaknesses (apart from lost territories obviously). In reality this political crisis happened. Here it cannot, because good ruler= strong realm while weak ruler= weak realm. Romanos Diogenes was good (or even very good) energetic and diligent Basileos but losing at Manzikert combined with internal crisis (long internal crisis!) resulted in loss of most of Anatolia.