Throughout the history of English, the word "man" and words containing it ("mankind," "manpower") were used to refer to all human beings regardless of gender. Dictionaries like the Oxford English Dictionary, which trace the development of words throughout history, acknowledge that "man" means "human" or "person," not just "male individual." Since words like "mankind" have already been gender-neutral for centuries, they do not perpetuate any gendered stereotypes or gender roles. They simply refer to human individuals. No change is necessary to get rid of the androcentric language because it is not inherently male-oriented.
From an etymological perspective, this viewpoint is false. "Man" has never been exclusively gender-neutral in English. While the Oxford English Dictionary does include meanings of "man" that are gender-neutral, some of which now obsolete, it also shows that this same word has referred to male persons from the beginning, too. Even in Proto-Indo-European, the ancient ancestor that gave English most of its words, the word for "man" refers mainly to a male person. Words like "mankind" have thus never been completely gender-neutral, rendering this argument invalid.