There are some contributing factors to the shift in inequality, a major one being that labor is now oversupplied compared to the post-war period, and the competition is driving wages lower. The U.S. has much higher immigration rates now, which contributes to the oversupply of labor. The late 1800s and early 1900s had similarly high immigration and high inequality. [1]
Whether the historical baseline for inequality is the best amount of inequality is a different question though. It's clear that as redistribution flattens the income curve there is dead-weight loss as highly productive people stop wasting their time doing taxable work. It's also clear that investing in children who would otherwise be malnourished or lack education or healthcare is a net positive for society. It's not clear to me that the current level of inequality is the wrong one - we're admitting a lot of immigrants who are vastly improving their life prospects as a result, the economy is growing, and technology is amazing. Spending more money on health care would have limited benefits [2]. I don't really have a strong opinion on whether inequality should be higher or lower (it's hard to find a good-faith analysis in these terms), but the Time article uses an arbitrary timeframe and doesn't shed any light on the question.
[1] See Ages of Discord for a much more detailed dive into this. http://peterturchin.com/ages-of-discord/
[2] Robin Hanson gives an argument with lots of evidence here: https://www.cato-unbound.org/2007/09/10/robin-hanson/cut-med...