As someone else stated, they do disappear but only from your view (IP address). Everyone else still sees them. In fact if you flag something, you'll see a "hidden" icon from your Craigslist view. If you click on that icon the ad you flagged will be there.
I find that things sell faster and I get more responses with Facebook Marketplace, but I still post items on CL just to get them out there. Sure, you'll get some scam replies but they're very easy to spot and then block or ignore.