If only it was so simple
Many people forget that the V6 Mustang out sells the Coyote by 2 to 1 in the USA. The "Mustang market" is actually many different markets (Which still includes many secretaries).
Some of those market groups really want a "great interior" with first class electronics and driving features. Many buyers are looking for a car that "stands out" in a crowd of cars. And others really want a "good value" car - price and functionality. Many of those groups don't "haunt" this board. I think the last group will be disappointed with the new Mustang. The price has seriously escalated in the last 5 years - over inflation - and particularly when it comes to the cost of new functionality. It would be very hard to say whether it was exterior style, interior quality, available electronics and features or price escalation that has hurt Mustang sales in the last five years. Only time will tell how these markets respond to the new "Mustang formula."
Not really sure what you're trying to get at here, but my comment was mostly just pointing out monthly sales figures alone. I don't think too many people would Deny the Mustang had better interior than the Camaro. Yet, it still sold better by a large margin. Likewise, performance was similar, but the Camaro still sold better. Lastly, the mustang was Cheaper, but the Camaro still sold better.
Looking at those alone.. It's pretty easy to narrow down why you can't beat your competitor.
A.) The general public wants something other than the mustang since it was sales leader from 03-08 with no real competition. So to set themselves apart they wanted something different from it.
B.) The mustang was just uglier than the Camaro and Didn't have IRS to boot.