YANBU. I am amazed by people who don't think this is a problem. This is where gender stereotyping starts or is constantly reinforced. It cannot be left to parents to constantly challenge and explain this...most of us are ourselves affected too.
Not every parent/grandparent will challenge in any case. It is not possible to counter every image like this, every day, several times a day which is what it takes. Some girls are encouraged to play with construction toys, cars, dinosaurs etc but once beyond pre-school stage they become labelled as 'tomboys' so it is seen as something different from the norm and there is an underlying message that it is not entirely appropriate for 'proper' girls.
And if you were to link these images to career expectations and earnings it becomes even more disturbing.
OP - have you raised your concerns with Argos? What did they say?