I have been reading some articles on digital transformation and change management and I am surprised about how little attention is given to the notion of comfort. The reason why change is hard is that it makes people feel uncomfortable. And when people are not comfortable, their confidence, morale, and productivity suffers.
At the very least, there is the loss of familiarity. Habituated routines that once hummed along on the edge of our consciousness all of the sudden require direct attention. Tasks take longer to do. Mistakes are made. The confidence of mastery can feel threatened.
There is always a group of people who benefited from the old way of doing things even if that way was inefficient or dysfunctional. Dysfunction can create jobs or mask poor performance so don't assume that everyone is onboard to eradicate it.
There is great advice for assessing change readiness and rolling out change. But be aware that the resistance that you feel is a primal tendency to seek and preserve comfort. In addition to your conventional change management best practices, focus your attention on people whose comfort will be the most impacted. These will be people who have developed mastery over specialized skills and knowledge or have accumulated power from the current dynamics. Think about what benefits would be the most motivating for those groups to buy in. If you don't have their support, you can count on their interference.
And remember to measure the impact of a change after people have had a chance to re-equilibrate and form new comfortable habits.