The writer calls it "a commandment whose observance is no longer possible". When was it ever "possible"? The Torah makes it quite clear that even when first commanded it "seemed impossible". Today we are not in the same situation as the pioneers at the time of Rav Kook's ruling. The difference over whether or not to allow the "heter mechira" has nothing to do with wheher it is "possible" to manage without it. It is an ideological difference.
ISIS kills 22 in Yemen's Sanaa, Aden; targets both gov't and Houthi rebels (Reuters)
from the article: Observing shmita sensibly