Gemora mentions, I think, R Yaakov who sent his son for a semester, then examined him and, after finding his learning lacking, told him to stay home and work the fields, and went to learn himself. He is them placed into a room with some nasty mazik that would kill anyone else – to clear real estate for the yeshiva, so he presumably had a good judgment. So, when you are suggesting that someone not learning much should sit in the yeshiva whole day – is he doing it at the expense of someone else who could use a stipend? Maybe someone who is working and learning, but a stipend will help him free a couple of extra hours a day for learning? Of course, if your community balabosim are supporting everyone who wants to learn, then it is not a problem.
As to those who learn 2 hours and don’t do much the rest of the day, those are worse of course, especially if they are paid to do that. But it is not a very good argument to say that someone is better than outright thieves.