Third party recruiter

I keep on getting email/ LinkedIn messages from 3rd party recruiters. They are normally from agencies or have their own company. They are not employed by companies which they seem to list in message that they are willing to set my interviews with. I had conversation with one of them a couple of years ago and it was waste of time as no technical round followed with actual company. Has anyone ever been successful setting up call and onsite interviews through these 3rd party people? I feel they seem to post interesting startups like cruise, instacart, neuvector etc