I actually completely disagree with you here.
Frida has not established a single identity in the 3 years she's been at Gucci. Looking at her collections from 2006 to now, there's no rhyme or reason to them, the only things they have entirely in common are the fact that they're geared towards trendy young girls and she likes to use prints. It's not just the surface look of things that people are questioning her about. It's that if you asked people to explain who the Gucci woman is and what she's all about, I doubt if you'd get a clear picture of her.
Donna Karan, Michael Kors, Versace, Rick Owens, Dries Van Noten, Nina Ricci, Ann Demeulemeester, every one of those labels has an easily traceable identity behind it that keeps whatever the designer does in perspective. How else do you expect that someone like Donna can veer between her Eastern spritualist world traveller stuff and her very polished, urban, tailored sensuality without it looking like two completely different designers had created it? And Prada does have a clear identity, even if you don't see it. Back in the 90s and early 2000s Prada was pretty consistent, her clothes were always slightly elegant, slightly feminine but also slightly off kilter and not quite "right". There was also, and still is at times, an underlying streak of frustrated sexuality to what Miuccia does, beneath the quirky, sometimes mumsy exterior. And despite all of the experimenting, Miuccia always harks back to that.
I also think at this point critics are asking quite literally who this Gucci woman is. What Frida designs is geared towards very young, very trendy girls who most likely cannot afford a $5,000 party dress or $3,000 leather leggings to go clubbing in. Even the simple printed dresses are probably way out of the average twenty-something's budget. So really, who is she designing for? Celebrities? The party girl children of millionaires and heiresses? Who else can afford, and has the desire and body to dress the way she pictures young women?
I think the key to understanding the criticism is this; just because the look of a collection is different each season doesn't mean the aesthetic is as well. It's also important to understand that putting the same pair of pants and the same jacket into a collection every season in different colors and fabrics doesn't equal consistency.
I mean, you may not get or agree with the criticism, but a dozen critics and countless tFS'ers can't possibly be pulling sh!t out of thin air every season.