Here’s an intriguing answer: no one would play or produce works by women:
But the main reason, I think, that there were so few female composers during the glory centuries of classical music is that composers depend on performing musicians and ensembles to play their works, and until relatively recent times, musicians, ensembles and musical institutions were overwhelmingly male.
There were a significant number of female novelists, poets and painters in earlier times. But if you were a Jane Austen, you could sit at home and write your novels. As long as you found a sympathetic publisher, you could get your books distributed and be acknowledged. Compare this to the situation facing Clara Schumann, one of the most celebrated pianists of the 19th century. She was also a gifted composer, though she mostly wrote piano pieces, songs, chamber works: things that she and a circle of musician friends could perform. If she had tried to compose symphonies and operas, even she, for all her renown, would have hit a dead end with male orchestras and opera companies, which would have been unwilling to champion the works of a woman. So why bother?
There would be several obvious female contenders for a list of top 10 novelists. Or poets. But consider this: Where are the great female playwrights of earlier centuries? Again, this is the same problem as with female composers: what theater company was willing to present plays by women?