I agree, this methodology would be a great way to identify deficiencies and ultimately improve product quality. It requires that the management be honest enough to admit, we don't have a best-in-class product, but we'd like to know where we don't, by how much, and we can use that info to determine how to get there.
The OP's suggestion is a good one. I wasn't being facetious either when I suggested that DL senior managers be compelled to experience the shortcomings of their own product from a customer viewpoint.
I'd bet that a contract provision that stipulates all DL managers over a certain level must use DL.COM to book their travel would very soon incentivize radical improvements.
The more layers of middle management insulate airline execs from the front line passenger experience, the more difficult it becomes a. to know what the real issues are and b. to understand how to address them in meaningful ways. DL seems to have some serious difficulties in this respect.