You're going to have a difficult time arguing that the economy was good for white men in the 1960s because it was bad for everyone else. Prosperity is not zero sum.

Perhaps it has more to do with the lower ratio of people crippled by household debt to pay for housing, healthcare, and education. There's nothing more K-shaped than debt, which is a lever for those with wealth and a weight for everyone else. It's a combination of bad policy and greed that put us where we are.