I had a thought which I think makes the federation look bad but what if it was mandatory that you have to work for you to get free access to food replicators and whatnot? Maybe the Federation has re-invented slavery? You can leave the planet if you want and go live the life you want but if you are on Earth, and other Federation planets you have to work. You do get to choose the type of job you want though you are encouraged to pick things that are on par with the stuff you learned in college or have a aptitude for or even past experience with.
I wouldn't go so far as to describe it as slavery, but I was thinking along similar lines.
Unlike a lot of assumptions I see, I don't get the impression that Federation/human society is some hippie-drippy paradise where anyone can have whatever they want and do whatever they want or do nothing at all.
I do think that basic needs would be provided for regardless of ability to contribute, but if you want more, you have to earn it, whether or not there's a measurable currency involved.
There would likely be laws and societal pressures, the latter of which would include indoctrination from childhood, that would motivate people to contribute to society via some sort of useful job that fit their capabilities.
Somebody upthread mentioned that maybe not anyone could be a marine biologist because there might be a limited number of positions available. I'd go further than that, using as an example the one career that we see in abundance in Trek--that of a Starfleet officer.
They work in a heavily regulated environment, one that's quasi-military in nature. They not only have to pursue the right type of education to get into this field, but be accepted into a highly competitive institution to get that education. Once they've gotten that out of the way, they have to work their way up the career ladder via performance and aptitude, which is reviewed by their superiors.
JJTrek aside, you can't just decide one day that you want to be a starship commander and have your wish fulfilled. The same would hold true for being a marine biologist, or holding any number of other professional positions. They're not gonna let some idiot with no medical training perform open-heart surgeries because hey, that's what he wants to do with his life.
That's my two cents, take it or leave it.