I think that caring for children, whether you are a SAHM or work in a nursery, is an extremely important role.
I also think it is important that there are women doctors, politicians etc. I would not want the entire medical profession to be male, for example.
But I don't see how the two things are incompatible. Many men in socially influential jobs retire in their fifties - so lose a decade of their career. Women who take 10 years out to be SAHMs also lose a decade of their careers. There is no reason why not working for ten years should be mean you can't progress in your career later, except the prejudice in society against SAHMs returning to work and the prejudice against promoting older people in the workforce.
There was a thread on AIBU recently about a SAHM who was having all manner of difficulties put in her way by various rules in her attempts to return to work as a teacher. Given that many women do becomes SAHM for a while, I would consider that regulational discrimination, as it has more of an impact on women as a group than men as a group. As a society we need to get rid of that kind of discrimination.
And a lot of it is just prejudice. If somebody took a couple of years out in their early twenties to stay at home with a child, that would be seen negatively by many, yet the same person taking a couple of years out to travel to South America or Thailand or wherever (the modern equivalent of the grand tour) is seen as doing something worthwhile.