There's an example on the first page of this thread......."Some people have teenagers in their 50s".
Err, I had a 5yo in my 50s. There are plenty of us with primary age children. People just don't think. 
But it exists in every sort of media. According to the tabloids, anyone over 50 has a gold plated pension
, we all own houses outright, had free university and now while away our time pottering. Rather than the reality of working full time, doing the school run and running a house like anyone else.
Ignorant, lazy reporting and frankly dim.
In covid terms, the country would grind to a halt if every over-50 flung up their hands and isolated. Most head teachers, hospital consultants, senior govt officials and senior police officers are in their fifties. But also thousands of carers, train drivers, nurses, supermarket staff, childminders, psychiatrists, water engineers etc. Without us society wouldn't survive.
In my last work place there was a discussion about whether we needed a tampon dispenser in the loo because there were only 3 women in the building and I was told I was too old to need one. By a 30yo woman.
. If only.
So mumsnet is no better and no worse than everywhere else. It would be nice if it were better.