I think it's fine that the Zoella website covers "adult content" along with some fluff, it's kind of like Cosmopolitan or whatever, and most people watching Zoe are no longer super young teens, and super young teens don't give a damn about Zoe Sugg so they wouldn't follow a teeny bopper Zoella, but there's a severe lack of a cohesive tone and that makes it feel like it's trying to be five things at once and doesn't know who its audience is or who they'd like the audience to be.
The writers aren't very good, on top of the missing cohesion in tone, so they often miss the mark too, sometimes their writing is too casual for serious things and takes itself too seriously for fluff articles. Bit of a cognitive dissonance there.
The way they handle their social made makes it all feel a bit zig-zaggy and dizzying. "Look, 25 cute things to do for Christmas!" veers quickly into "Women speak about their troubles conceiving" turns to "Book club time!" and then goes to "VIBRATORS, HOW FUN". Or something like that.
I don't know how they'd be able to solve their issues and actually grow their following without taking the website a bit more seriously and investing in good writers, even freelance ones, and discussing things that matter broadly to female identifying people. Yes, keep the listicles, listicles are fun sometimes when they're well done and relatable, but also come up with good interviews, articles, etc. Like Buzzfeed, Hello Giggles, Bustle, etc.