Look and feel is important, but consistency is more important.
And Microsoft is constantly changing when there is really no value in the change. In fact, each change I have seen over the years has made the product less user friendly.
Your Outlook classic look and feel was great, there is no reason to change. In the new version you put the search field up high, presumably that is because you think we will all want to use it most of the time. However, I knew where the search field was before and will use it if I need it, changing it's location is not at all helpful, and now looks messy. Please put your energy into improving connections and change the look and feel, only when absolutely necessary.