When something is secularized, it means it is changed to be less connected to religion.
Secularizations can be good or bad, depending on how people feel about religion.
Examples:
The secularization of the holiday removed all religious symbols.
The secularization of the school system meant no more prayers in the morning.
The secularization of the government buildings was controversial.
The secularization of the event made some people happy and others sad.
The secularization of the tradition was a big change for everyone.
The secularization of the ceremony was a big deal for the whole town.