They are not. Simple as that. Why? Because they are TOYS. Toys are meant to entertain and make a kid have fun, if he/she takes the fun to another level as to try to be like the doll at that point it is a parent's responsibility to not allow that.
Yes, the fact that they are toys is true. But the children who use the toys sometimes want to dress up as the dolls (the little girl I babysit has a Barbie dress that's her size) and see the dolls as 'pretty'. I think that the image never truly leaves them and that body image follows them through not only dolls, but magazine ads and clothing mannequins so they never really have another image to think of as 'pretty'.
And so do girls who own a Cabbage Patch, and a Cabbage Patch is not physically attractive. The little girl wants to 'dress' like a Barbie and not one, now in the case that she wants to be one, as I previously mentioned, it is the parent's responsibility to make the child understand that she cannot be that way, and either way one of the main reasons a child wants to be like a doll is because they idolize it, not because they see the "beauty" of it, at a certain point of their lives they will let that feeling go. And although yes, other things in society as magazine ads and clothing mannequins create that certain image that follows them, it is the maturity as they grow up that will make them forget. And yes, they and everyone can see the image of 'pretty' anywhere because there isn't a specific image, it is called: Reality.