In what way is concrete a sustainable building material? It's a huge carbon emitter, a poor insulator, concrete production is devastating to natural habitats turned into sand quarries, etc. Plant-based construction materials, e.g. hemp, seem to be vastly superior on every ecological consideration.

Plus, an unreinforced concrete dome has to be one of the inherently least population dense structures, and density potential is probably as important a consideration in sustainability as actual construction techniques.

Edit: not necessarily a dome, but also not able to safely scale the structure very high with this technique without losing the only purported advantage, the low labor cost.