No. UDK over past years didn’t changed much, because all developers moved to working on UE4.
UI changed quite a bit in UDK when it was still developed. There were added new things, mix and matched C# and C++ (WPF and WxWidgets). The base UI didn’t change much and that is the fact. Neither UE4 base changed much since beta.
I think you really don’t have past game development experience.
UE4 is as stable as game engine can be. Other engines make breaking changes all the time, without looking back.
In game development trying to stay backward compatible means one thing. You hurt engine development, and you hurt end users, by old things polluting code base.
Fortunately game development is the bastion (yet) (along with Linux kernel), where backwards compatibility is not priority. When something needs to be changed, to be better and break other stuff. So be it. Adjust or don’t update to new version.
Yes it can be annoying. But I’d rather have it, than being stuck with rotten code.