Well I'm not an old nanna, and I still want to be called Mrs.
It's interesting to note that the adherents of Miss and Mrs are more than happy for others to have the choice to be Ms, whereas some of the adherents of Ms will only be happy if their choice is the only choice, no matter whether that upsets other people.
Frankly, if anyone is treating me as second-class because I am a Mrs, it is some, not all, of the people who espouse Ms - other women, not men at all. Is it really feminism, to treat other women as second class because their choice of title is different to yours?