The thing about the deeply disturbing societal issues surrounding people calling themselves Mrs or whatever, are simply not deeply disturbing to large numbers of people.
Some people have opted to be Mrs, because they have never considered the background to why women take their husbands name. They haven't considered this, in the same way that they haven't thought deeply about socialism or liberalism or a variety of other things which actually do explain how we are where we are today. They just aren't very interested.
Other people have thought through these issues and understand them and still choose to become Mrs. It is actually possible to do that and not a sign of total stupidity or ignorance.
Other people have thought through the issues and chosen not to become Mrs. That too is fine. However, when the self-labelled enlightened, paint everyone else as totally ignorant, I see arrogance and a lack of empathy rather than enlightenment.
Without doubt, the fact women had no choice but to take their husbands name and lose their own, was part of society not seeing women as equal. Much of our history has roots in subjugation of different groups of people and very different values to those we have now. When we look at the past, we do need to see it in context and recognise that things in the past were different...no doubt people will find many things we do and values we have odd or wrong, in the future. Society today is a product of the past and we move forward unevenly, even in big areas of change. Yes, changes in social attitudes are probably slower than we might imagine, or even hope. We are not so far from the times when women themselves considered themselves men's property or when most accepted unquestioningly that the only option was to become Mrs with the man's name, that connections to those ideas and even enjoyment of them has gone. It will take longer and it maybe that for many many many years to come, the majority of married women will still choose to be Mrs. Yes there might be deep seated values within society that drive them in that direction......but aren't all of our actions really driven by such widely accepted understandings of values.
Anyway, as I said ages ago, I think the school poorly worded their communication with OP about her title. I do not imagine they intended offence at all, but whoever wrote the email simply wasn't hugely articulate. I suspect it was an admin issue of the school programme not accepting the title chosen, or needing spbespoke entering that they hoped to avoid. So yes, it was poorly worded (but so are lots of communications) and yes, the fact OP said she still wanted to be Ms should have been logged, but somehow wasn't. She can inform them again and make clear she feels strongly about it. If she wants, she can enquire as to why they asked her to change. If she wants, she can tell them that she found the request inappropriate and why. Perhaps they will then re-word it or simply not send the request in future. Job done.