Yeah. I don’t get the objection.
I’m Catholic and I’ve had my feet washed by our pastor on Holy Thursday during the Mass, and I’m female. I can’t imagine why this is a problem. It’s a ritual wash, not a massage, for heaven’s sake.
It is a problem because, as post 25 points out, the rubrics say “viri”. Yes, the ritual could be changed, but ignoring it is not the same thing as changing it. There is a quote from Seneca that I have on my bulletin board at work, that translates roughly “No one is able to rule unless he is also able to be ruled.” Humility is a good thing, but an important aspect of humility is seeing one’s proper relationship with others. If the Pope appears to believe that he needn’t follow the Church’s liturgical rules, he will have a hard time convincing those who notice this to take him seriously when he tries to get them to follow any dictates laid down by the Church.
That said, he deserves some slack because he is a Jesuit, and the Jesuits have never been known for good liturgy. The old canard “lost as a Jesuit in Holy Week” would seem to apply.