The whole is greater than the sum of its parts. Often you need to disregard the detail and minutiae of existing processes to set a better course. The goal is not to avoid short or even medium term pain or even unintended consequences at a department level, but rather to steer the company in a new direction. Processes should adapt or be thrown out to achieve the new direction.
This is not too dissimilar when you realize a software architecture is holding you back. You don’t try to “save” all the existing functions, modules, layers, etc. but instead are happy to discard or replace them given your top-down vantage point of the system and where it needs to head.
You still need to manage that change to varying degrees. For every organization which can shift on a whim, there are many more which require mitigation. Normally, there are a lot of things carried forward for internal or external reasons. Developers tend to discount the amount of effort from other actors in the system because they don't understand all of their priorities and which map neatly versus not.
And then you go out of business because you were busy rewriting Netscape Navigator while Microsoft was churning out new versions of Internet Explorer.