I don't think GP is advocating to keep the land undeveloped. They even go so far as the point out how the area makes a lot of sense for developers. The problems they identify seem to be 1) the reckless abandon to which developers are damaging ecosystems 2) an economic situation that allows developers to benefit significantly without these benefits necessarily passing into the community 3) the significant challenges of rapid population growth and 4) the fact that this development threatens their home. These are worth discussing and balancing against any benefits.

I also object your false dichotomy, and the idea that employment and "progress" (I doubt we can ever objectively make such a declaration) are zero-sum here.