I've moved into a new (to me) house, with lots of issues.
When I shower, unless the windows are wide open, the room gets so steamy that you genuinely can't see the other side (like one of those spa steam rooms). An electrician has checked the extractor fan and says it's working and a good quality one, but that you have to have windows open when you shower.
My last 2 homes I never needed to keep the windows open to reduce steam. I did a daily open, but didn't HAVE TO in order to shower.
So..
YABU : The extractor fan will never be enough on its own and everyone always has to keep the windows open
YANBU : The extractor fan should do it's job and not be reliant on windows too.
I'm genuinely interested in the experience of the MNers.