Well you're right in the sense that it wasn't 'the' problem...but, at least for me, it was the harbinger to everything we're seeing today.
First thing he talked about when he took over was 'building through the draft'...well he should of noticed how little draft picks the Habs had the years before he took over (2008 to 2011). If building through the draft was his mandate, he should of been trying to sell off as many of his veterans as possible to acquire additional draft picks.
That means, Plekanec, Gionta, Gorges should of all been moved before or at some point his 1st season.
See he did do some of that when he took over, moving Erik Cole, buying out Gomez, he just didn't finish that work. The draft picks he could of potentially acquired for those players would form the base of our team today.
I'm not trying to be revisionist either, I was strongly advocating that approach at the time. But as usual with the Montreal Canadiens, after coming off a terrible year, the most important thing was to qualify for the playoffs the following year, short sighted approach.
The goal wasn't to build something sustainable...just get into the playoffs as soon as possible.