You completely miss the point, by your logic if Scotland and England were the only playable nations the game would still be "Crusader Kings" and would still be what we brought. In addition, they have made the Muslim nations fine, they work just like all others work but they want to make you pay more for what is there, to fix your point this is like buying a car and paying extra to get the trunk open.
No, it's always been said you can only play Christian nobles. What people finds baffling is there's a game called "Crusader Kings 2" which is advertised with the line "Take on the role of a Christian noble and carry them through the ages from Count to Emperor via the line of succession" and then you get angry when you find you can only play as a Christian noble. Whatever gave you the idea you'd be able to play non-Christians? The quoted line is on our web page, on the game's box, on the Steam store page etc. At no point have we ever said you could play as a non-Christian noble. On a similar note, if you bought a game called "Kings of Scotland and England - A game in which you can only play the aforementioned Kings!" people would be pretty confused if you turned up on the forum to complain you can't play the French. If you just buy random games and then get upset when they don't have the features you imagined they might have you have no one to blame but yourself.
Do you even own CK2? I note you have not registered it.