What's happening in Afghanistan is "news". During the US occupation of Afghanistan, the Afghan government had been making progress in its treatment of women. With the Taliban taking over, much of this progress is expected to be reversed. This is a sudden, dramatic change for the worse, so it's natural for it to receive lots of coverage in the media, especially since both the past progress and the recent reversal are direct consequences of US actions.
What's going on in Saudi Arabia is just the status quo in that country, it's not news. When there are changes, the media covers it -- when they gave women the right to drive 2 years ago, that was big news.
As an analogy, in the past few weeks, there have been a couple of incidents of coyotes biting children in my town (a Boston suburb), and this made the news. I'll bet there have been many incidents of dog bites during the same period, but none of them were in the newspaper.
It's also the case that women have better lives in Saudia Arabia than Afghanistan. Even before the recent action of the Taliban, female literacy in Afghanistan was only 17%, versus 45% for men there (reference), and 93% in Saudia Arabia (Wikipedia).
Georgetown Institute for Women, Peace and Security ranks Afghanistan as one of the worst countries for women. (reference)
In the above ranking, Saudia Arabia is 99th place, while Afghanistan is 152nd out of 153 countries ranked. The list is from 2017, before the Saudi reforms of Mohammed bin Salman.