Agreed with many of the sentiments above.
One of the joys of traveling places is trying new foods and restaurants. Whatever they serve on the plane won't match what I'm hoping to get at my destination, so I don't see the need for them to try to compete.
One of my favorite meals that I had on DL was back in the Michelle Bernstein days (I know, I know), and it was basically pasta with red sauce.
The food on defunct version of AZ was pretty good as well, and it was served from a cart. Again just simple pasta and/or meat dishes.
And a perennial favorite DL dessert was the ice cream sundae. Just vanilla ice cream, hot fudge or hot caramel, whipped cream and a cherry, and people loved it.