If you read my post again, you'll see that I identify a number of reasons, most of which are down to an embedded system which acts to marginalise women. They get less promotion from publishers and booksellers, their books are less likely to be reviewed in print and on line, their work is less likely to be assessed seriously. Joanna Russ' short book How to Suppress Women's Writing provides a good introduction to how this works.
Quality is often irrelevant. Male writers' work can and sometimes does decline in quality, too, but this tends to be ignored or excused.