Why does Gulliver censure Balnibarbi?

Gulliver censures Balnibarbi because although its people all seemed to be busy, they failed to produce anything.

We passed through one of the town gates, and went about three miles into the country, where I saw many labourers working with several sorts of tools in the ground, but was not able to conjecture what they were about: neither did observe any expectation either of corn or grass, although the soil appeared to be excellent. I could not forbear admiring at these odd appearances, both in town and country; and I made bold to desire my conductor, that he would be pleased to explain to me, what could be meant by so many busy heads, hands, and faces, both in the streets and the fields, because I did not discover any good effects they produced; but, on the contrary, I never knew a soil so unhappily cultivated, houses so ill contrived and so ruinous, or a people whose countenances and habit expressed so much misery and want.