Fair enough but you are comparing apples with pears.
Energy levels vary dramatically between forty and sixty years olds. It’s hard to describe it, or understand it, when you haven’t experienced it.
Therefore your mother at full pace can do less in a day than she used to achieve twenty years ago, But that doesn’t mean she is not still as active or busy when she is using her energy to full capacity, even though she can achieve less than you do in the same time.
Batshit is a bit of an unfair description given that none of us can help the ageing process or slowing down! It comes to us all in the end.
Obvuously, you know your mother best, but what she may mean is that she has enough on her plate currently given how long it takes her to keep the house clean nowadays or how much her knees ache or whatever,
People can become less adaptable, and less resilient to stress when they age too, so need longer to recover sometimes.
Also, you never know, people do engage in intellectual pursuits that do not manifest necessarily as “busy” to others, such as writing a book. Could your mum be crafting the next bestseller? 😀
Edited: obviously I’m just kidding about the novel but I firmly believe in the rights of older women, who have worked and facilitated family life for others for two or three decades, to use their remaining time as they wish, either creatively or sitting on the sofa with a colander over their head. They have earned it!
Having said all of that; I do think the age at which you have children makes a huge difference to remaining energy reserves. If you have supported late teens and young adults in your sixties, you usually need a bit of a rest before having full-on engagement with gc!