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The simplifying or outright dismantling of liturgies has been in train since the beginning of the Reformation, particularly as it started to unfold in Switzerland under Huldrych Zwingli. From the linked Wikipedia article:
Shortly before Easter (1525), Zwingli and his closest associates requested the council to cancel the mass and to introduce the new public order of worship...The sermon was the focal point of the service and there was no organ music or singing.
They still did describe the order of service as a liturgy, but there was a radically new conception of what that meant.
In many ways, Zwingli was more "Protestant" than Luther - his rejection of the concept of the real presence in the Eucharist and limiting communion services to four times a year was a major step towards a "de-liturgized" service.