I say that Ford's vision of Gucci was was genuine because it was always very apparent that what he sent down a runway, sold in stores, and featured in ads was always what he truly believed in. He didn't resort to banalities in his clothes, nor did they look like they could have any random label inside. They were recognizable with a very, very strong and precise personality built in. As you said, it was about an aesthetic, a lifestyle which, imo anyway, is much more than just clothes. He was one of a handful of people who could manage to make even something mundane seem new and exciting.
Giannini's Gucci woman doesn't have a personality, at least not a very convincing one, nor is she doing anything that doesn't already exist. She "designs" a bunch of clothes that other designers have already done a million times over to the point that they're not only a cliche, they're lazy go-to ideas for any number of truly untalented designers. Her "aesthetic" caters to two sets of people; the men and women with enough money to spend a ridiculous amount on clothing that you can buy at a much lower price, for almost the same quality, in any number of high-street, mid-market retail chains and large department stores before they're even shown on a Gucci catwalk and the men and women running the company who's sole concern is profit.
I don't know about you, but I'd prefer to have a vulgarity laced p***y parade of actual luxury goods instead of the boring bottom line coming down a runway....at least it gets your pulse racing for a split second.
As for why I believe this isn't truly cool, borjacapella put it much more eloquently than I would have. But basically, making an effort to be cool has the exact opposite effect.