It means that there are 8,000 ads. That shows that lots of people are trying it (or a few people are posting thousands of ads each), but that doesn't mean that many of them are successful. Maybe they're all successful, maybe not. But the more people there are in a marketing niche, the less room there is for more.So? Don't you know what that means?
"Saturated" is another way of saying "it works for many people"... but please let that discourage you.
Try it if you want.