Strange but true, the yeast is not asked to be the dough, nor the mustard to be the jackfruit. What is expected is that the yeast be the best it can be and do the most it can do. Being in the minority it is asked to be a catalyst in the whole dough, not become the majority! It is to transform the whole of the dough by being in the whole mixture, not outside, not away, not detached.
Perhaps a lesson we ought to learn: rather than spend all our energies on increasing our numbers, as Christians, we need to deepen our own understanding of our call, and thus be agents of transformation in the whole society. Statistically the world may then not be 'Christians' but in spirit and in truth, it will certainly be!