The Fantastic Four is being cancelled due to damage suffered under Milliar and Matt Fraction.
After Millar left the FF book, Hickman took over, and he produced what many people consider to be one of the best runs throughout the book's history. His run brought a lot of acclaim and attention to the book. Sales might have even gone up. I would hardly say that Millar "ruined" the title. It didn't end when Millar left the book. And so on for other titles and books. Remember Heroes Reborn, or the Clone Saga? Everything recovered after a while. If you ask me, what's really hurting the industry is all of these constant events/revamps/crossovers that they seem to do at least once a year. A status quo can't be too exciting if we know that it will only last a few months. At least Civil War (As disappointing as it was.) had some long-term ramifications.