It's always been a kid's show. But it is possible for it to be a kid's show and a good show. Unfortunately it is now a kid's show but not very good.
And I don't think the problem is Smith. He's a really strong actor and his version of the Doctor's character is not inherently bad. I think it's mainly down to poor writing. I agree with chernid - everything is overly romanticised. Maybe it's just that Moffat thinks kids can't understand stories which aren't about love? Because his writing for Sherlock (for example) doesn't seem to have the same problem. (Though the sexism is still evident there.)
But I think the main problem with his writing in Doctor Who is that he tries to create overly complicated overarching plot stories, at the expense of individual episodes. I'm fine with a significant overarching plot because it brings the series together, but it has to be woven together carefully within the episodes, and with Moffat he seems to have trouble doing that. It ends up confused and messy in my opinion.