While "No" is not enough, it can often be a pretty good start towards a positive program. A lot of benefits come from making policy by saying what we have decided that we will not do.
Measure J, for instance, the Santa Cruz County Growth Management referendum measure adopted by the voters of Santa Cruz County in 1978, provides protection to prime farmland in Santa Cruz County by prohibiting the use of such farmland for anything other than farming. By saying "No" to something that shouldn't be done, we can often achieve the positive results we seek.
Since "anything is possible" in the human world that we create, a decision not to spend our efforts and resources in particular ways can end up focusing our energies in the positive directions we'd like to pursue.
Don't give up on "No." It's one of the most powerful tools we have to shape the world we want!