To an extent, your interpretation is correct. But it's not really what's meant by that here (and I think you know it :) )– there are some (many?) 20-somethings

To an extent, your interpretation is correct. But it's not really what's meant by that here (and I think you know it :) )– there are some (many?) 20-somethings out there who work as <low maintenance menial job>, because "I can always worry about a career when I'm 30" and "I'm just going to do this for a couple years while I find my thing". I personally know people like this, and you probably do as well– that's the kind of attitude that was referred to in my original sentence.