I think you meant Age of Reformation, not Revolutions.
Come to think, I'd also put Russia as RoTW because they have one hell of a time getting institutions.
Oh yes, Unite your culture group is silly hard and outright impossible for nearly every culture group. I'd rank that as the hardest amongst all Age Goals.
Yeah, Age of Reformation.
And actually, I feel that many of the Reformation's age objectives have issues:
Join the Reformation: Literally unable as most countries. They could at least add Embracing the Counter-Reformation to it, and perhaps even flipping to Sikh.
Humanist or Religious: Reliable, BUT it heavily limits idea group flexibility during the early game.
Convert Provinces: Reliable for anyone not in the middle of a religious area unwilling to flip religion.
Colonial Empire: Ahahahahaha. I've never completed this objective once, not even in my Spain runs.
Converted another Nation: See "Convert Provinces"
Asian Trade: Basically exist only for the Asians and perhaps Portugal. But if you start in the region, relatively reliable to get, even if not always right from the start of the Age.
Unify Culture: Lol no