"Sustainable" is a religious term. You can substitute "sacramental" wherever you see it. This is because it does not withstand the application of rationality. It requires, instead, a faith which is not borne out by past history.
"Sustainable" is a positive attribute. Sustainable is clearly better than unsustainable, isn't it? Who would want to engage in any unsustainable activity? There are, however, activities which are bad that should not be sustained. Take, for example, sustainable whale hunting, or sustainable pollution.
Sustainable is good only if the activity is good. The people who preach sustainability simply assume that the activity will be good forever, unchanged. This misses out on two possibilities, however. First, that the goals of the activity may be achieved through different methods (e.g. unsustainable fishing may be substituted for by fish farming, and leaving alone native fish populations), or the activity may be changed from being considered good to being considered bad.
There was a news report on NCPR about "sustainable agriculture" this morning. That prompted this entry even though I didn't hear it (had to walk the dogs). My assumption is that "agriculture" is considered to be a good thing, now, forever, and always. Yet just as we consider whale hunting to be bad, perhaps some day we will consider agriculture to be bad? Maybe we can grow the food we need hydroponically under grow lights, leaving the vast bulk of the land to go back to wilderness?
I contend that everyone who thinks "sustainable agriculture" is good would also think that returning farmland to wilderness is better.