I don't see any reason why you wouldn't be able to completely slack off. But I can see a host of potential reasons why you wouldn't want to.
i'm using extreme slacker examples here......so lets put it another way, does Picard's brother make wine because he enjoys it or because he needs to make profit or to trade......obviously the former......then you turn up one day and tell him that we need someone to clean star ships and do some hoovering.....you honestly believe he's gonna say yes, ok i have a civic duty and will comply.......sorry no, i just don't accept it as a remotely realistic possibility.....he enjoys making wine and living on his farm (private property in the future?!) and has absolutely no reason to give that up to do something he doesn't want to do
we've established that not all menial work is automated and we've established that no one has any real imperative to do that menial work voluntarily so my underlying point is.....this is clearly a flaw in the...."money doesn't exist theory
sure there'll be the few who won't care and will just sit around on a holodeck and eating junk food, but I don't think the consequences of that kind of choice will be very appealing to many. .
again, the example of sexing it up and being a layabout was an extreme example to hammer the point home but it's turned into a bit of a red herring.......if i lived in that society for example, i would probably be very pro-active, motivated and interested in doing worthwhile things with my life such as studying something or exploring space or being an architect or whatever.....the point is, if i can be architect (even a bad one who doesn't get commissioned much but it doesn't matter because i have no bills to pay or material concerns) then why would i agree to clean your ship.....unless there is something in it for me
and no matter how many times people tell me that we'd all be much nicer, more responsible and have a greater sense of civic duty in the future, sorry, i just don't accept that as a convincing explanation