While I am not a qualified teacher, or even an experienced meditator, I do not agree that the Buddha’s position was that one cannot actively develop mindfulness, concentration, and wisdom. In fact, it seems to me that the Buddha did indeed encourage his followers to develop these things.
To begin with, the Buddha taught that whatever is impermanent is stressful, and whatever is stressful is not-self. The goal of Buddhism is to essentially take this [analytical] knowledge, along with a specific set of practices, as a stepping stone to what I can only describe as a profound psychological event in the mind. Nevertheless, that does not mean that I believe the teachings on not-self are understood to deny individuality (MN 22) as well as individual effort (attakara), far from it.