You're going to change how the software interacts with the user because you got a nifty tool kit upgrade? Because you went from Programing Language Not Currently in Vogue to Programing Language De Jour? You think the software should work on a desktop bolted to a desk at a shipping department just like it works on your child's IPAD? The latest iteration of homo-sapiens isn't fawning over the fully functioning design? You should get out of programming and move into a more useful career: Ocean water garbage removal. Sure, it might seem like a good idea for the UI to be changed so that some feature can better fit in to the latest UI concept, or even be cool to the latest crop of budding consumers just entering college, but changing how something works is a huge deal - not for you programmers, but for the millions of people that actually use the software to get things done.
Software is a tool, not an art project to stick in your effing portfolio. First off, UI design must be functional and then elegant. It matters not one wit if the UI is pretty or even if it wins awards for its looks if the thing doesn't effectively and efficiently do the damn job its supposed to do. Changing the UI design, especially deleting functions or moving them around is equivalent to breaking the software. It doesn't work like it did yesterday and NOW it is neither effective nor efficient. Now it requires learning, and then re-learning, and if used often will require UNLEARNING the old way -- something humans don't really do well at all. If you can't make the changes you need to the code to both improve the underlying performance, add a feature, appeal to the "youts of 'murica", and still keep the old stuff where it was and working as it was, then get out of programming. Just quit. Save me the time and aggravation of figuring out what is going through that two cell based life form you call a brain while I have a multi-million dollar project idling because the people working on it can't figure out where those vital features are now located or worse deprecated, a fancy word for too fucking lazy to keep a feature working.
And don't get me started on the "what we changed in the latest upgrade" document. I get better change logs in World of Warcraft patches than any other piece of recently "upgraded" software. Hiring some stoner you met at the Weed Works to write "We changed stuff" and hide it in a PDF buried more effectively than landslide victims in Washington State, isn't sufficient so mitigate the change chaos. SO stop lying to yourself about how it's really okay and people will get over it. No THEY WON'T. We don't get over being blamed for the consequences of some anonymous jackass programmer's design changes. We get to SUFFER because of it. And that is NEVER going away. We remember it because you're the reason the budget was blown, the system failed, we missed a deadline because the software got upgraded. We didn't get new training because we had to spend the training budget on teaching folks how to use the upgrade instead of something that might actually get our productivity up. Yeah, change that UI, will ya? We need more stress and aggravation.
Remember when Microsoft moved the print function in office? That little bitty change was a juggernaut of wasted time and effort trying to first, figure out where this common function had be re-located, and then passing that knowledge on to people who really only want to print documents as a part of their job. That's right, printing documents was the core piece of their job and one night it got upgraded into some other part of the software. Brilliant. Now we have employees approaching retirement age who already hate computers and software trying to figure out how to print documents so that they can ship product to customers while the trucks are idling outside the office at $200/hour demurage causing the shipping department to watch their quarterly bonus vanish as they struggled to figure out how to PRINT. Yeah that was a great move. I'm sure those guys would love to buy the UI changer a beer.
It is axiomatic in our economy that many of the people who use your software HATE it. They use it because some corporate guru in IT approved the decision by a manager who based the purchase on the cost of the software, the attractiveness of the sales representative, and how good the proposal dinner was. Now you want to fix the UI because you disagree with the design decisions of the last artsy fartsy "design" committee and your new shiny spiffy design will be sooooo muuuuuch betterrrr. Broken. Days and days of hair pulling. Overtime expended. Cursing. HR getting involved because the work atmosphere turns toxic - well that happens when the underlying assumption governing bonuses gets broken and management doesn't care. Well they care, but not about the upgrade issues, just the fact that product isn't getting out the door as fast as yesterday. THAT they care about. Yeah. Great times. You should come work for us next time you change the UI.
So let me restate this in the strongest possible terms: YOU SHOULD NEVER CHANGE THE UI. If you start changing the UI, quit the project. Go to Tibet, become a monk. Join the army and specialize in bomb disposal. Buy a weed farm in Colorado and spend the rest of your life toked up under the awing of a porch waiting for Jeff Sessions and the Black Helicopters. I don't care. Just don't change the fucking UI.