It might be that historically one of the main reasons for the weakness of the shemitta laws was because the leaders of those ancient societies instinctively felt how it weakened their own prerogatives in the public sphere, and so they were disinclined to engineer the necessary institutions to make shemitta work.
The leaders of ancient societies were disinclined to think through the demands of a proper implementation of the shemitta institution – be they political leaders, economic leaders or spiritual leaders – because the entire shemitta project threatened their own purchases on power in society.
If that be so, if shemitta were a threat to the regular, institutional leadership of society, then shemitta should be understood as a deeply radical social institution. What that means is that shemitta is quintessentially a grass roots institution designed for the lower classes, and shemitta needs a vigorous grass roots to keep it fresh and wholesome.
Shemitta and yovel are the grass roots hiatuses during which time the ordinary citizen, the am haaretz, the lower class person, has as much say in the conduct of civic society as does the leadership. It therefore falls to the grass roots to recognize in shemitta the potential for this enfranchisement and empowerment, and to work throughout the six ordinary intervening years to foster a vigorous experience of shemitta and of yovel.
Shemitta needs to be administered from the ground up.