The Universe is ever changing. True, we stand as a pillar of stability but we need to show some adaptability or become obsolete like what happened to the primal faiths.
The Reformists are concerned with the day-to-day workings of the Church rather than the nitty gritty details of Faith and Tradition; often taking a more practical approach to ethics.
The Reformists are a unique Branch, with no set dogma or beliefs; they stand together under the very idea of change and adjustment itself. Accepting of all cultural backgrounds it would not be unlikely to meet a Reformist, from all through the Empire with a variety of beliefs and ideas.
Currently in this coming time of turmoil and the shift of power occuring with the Emperor's death, The Reformists have an opportunity to ensure the Churches strength through adapting to the current time.