My suggestion for an explanation for the omission of Carol is based on this part of the interview about the "Timeless" Marvel Mural
"I've made the argument the entirety of my career that what I was trying to embrace was the timeless versions of characters," he says. "Because when I got in the business in the late '80s -- in '89 -- most of the published characters were going through a transformation of one type or another, usually meaning they were being redesigned -- new costumes. So, creating a composition like what I've done here is my of way of making the case for, 'These are the eternal versions of these characters.'"
Carol as Captain Marvel might not fit into his "eternal" vision of the character since its fairly recent and still struggling for legitimacy for many readers. And then to portray Carol still in her Ms Marvel incarnation would conflict with the company line, so to speak.
WOW. I'd somehow never seen Ross's Carol Captain Marvel design. Thanks for putting me on the hunt for it. From "Marvelocity"