Between the author patting himself on the back for coming up with "don't do things for no reason" and "don't make things worse," he provides this criteria:
> The only time a UI should be updated is if it impacts the ability of a user to actually use your application.
This criteria can be rewritten "only change to make improvements," but this is an eternal challenge with anything.
The previous UI wasn't handed down by god. It, too, was designed, and the only thing it has going for it compared to the global optimum is that it at least exists. And like any other system, it was built under different requirements with different unknowns. It accumulates debt and falls into the same traps of any other rewrite. Most importantly, it has to interface with actual humans.
I can sympathize with their rant over grating redesigns, but it's too easy to lambast things that go wrong and then plant your flag of "Yep, don't do this. You're welcome." It contributes to the toxic cynicism rife in our field.