That gets at something I've written about before; though I've focused on income rather than wealth. By any reasonable definition of what the "middle class" is the middle class is better off now than it was back in what people think of as the golden days of the middle class.
In 1963 the wealth level at the 50th percentile (the middle) was $41,028 (in 2016 dollars). In 2016 it was $97,300. 2.4 times as high.
So by what calculus do we say those at the "middle" were worse off in 2016 than they were in 1963 when they had almost 2 1/2 times the wealth in 2016 in inflation adjusted terms than they had in 1963? It's ridiculous.
This thing of focusing on the "gap" is ridiculous.