Several traditional Buddhists have criticized mindfulness training. At first this seems a bit odd, but reading the whole critique explains the problem they have. It wasn’t mindfulness practice per se, it is mindfulness only as a way to cope with the stresses of modern life or even to sharpen the predators’ edge. The Buddha taught a way to transform individuals and society, not to prop up an unjust, predatory system.
Living by Meditation Alone lays out this view in more detail.
When one examines the place of meditation in the Vajrayana in particular, one finds again that it is not considered a self-sufficient means of spiritual accomplishment. It comes second in the triad of view, meditation, and action. View signifies the correct vision of reality that the Vajrayana master imparts to the student, and meditation signifies the subsequent development and stabilization of the glimpse afforded by this introduction. Thus, it is only through both view and meditation, together with their enactment and testing in action, that one could even approach spiritual accomplishment.
Note: Vajrayana is the Tibetan branch of Buddhism. This teaching is central to all traditional Buddhist traditions. It is only in secular, Western Buddhism that meditation only practice is encouraged. Ethics has to have a place in the teaching or you get the perversion of the samurai—calm, efficient killers and militarism, e.g. Japan leading up to WWII.
In every religion, there is a tension between the institution that wants to cozy up to the power structures, whether empire or free market capitalism and the founder’s way of transformation, compassion, and justice. Certainly we are currently seeing this also in Christianity, e.g., the evangelicals and other conservatives joining with political right.