I think it is not just journalism. I do a lot of interviewing, as a lay panellist, for a particular professional group and am always struck at how few middle aged women there are. There are men of all ages, and a good proportion of younger women but middle aged women are rare.
My pet theory is that is is a combination of past sexism having suppressed the good ones earlier in their careers, current pressures on esp women in the sandwich generation dealing with teens and elderly parents, and middle aged women having fewer fucks to give and thinking twice about taking on extra responsibilities for no more (& sometimes actually less) money.
In journalism I suspect there is additionally present day sexism and thinking us dull old cows have nothing useful or interesting to say. How wrong they are.
Anyway @NoBinturongsHereMate get sharpening your quill!