Why is China, the world's 2nd largest economy, not part of the G7?

China, the world's second-largest economy, is not part of the Group of Seven (G7) countries because the group represents "advanced liberal democracies" while China is an "authoritarian single-party state". Also, China's economy is still considered developing over its relatively low net wealth per adult and HDI. The G7 was formed in 1975 as a platform for world's leading industrial nations.