I agree that arbitrarily forcing crises on player is bad for the overall enjoyment of game, the appeal of sanbox has always been choosing you own way to play.
I think that the best way to handle the crises would be to make each one triggered by a short quest chain chosen by players at their leisure – say, recovering 3 powerful artifacts from tombs awakens the undead, raiding settlements for a noble house triggers war between factions, etc.
This way you can have them or not and exactly when you want to, making everyone happy… I think?
