That's a non-trivial amount of hard work going down the drain right there. I'm not saying it was the right thing to do, but XUL and the component architecture were major reasons Mozilla took forever to be released, and then forever again to become usable. And then a major reason why Firefox extensions became a thing long before using web tech was an option. I tried to find uses for it back in the days, read a book an…
They only get so complex when people insist into plugging a square into a round pet, like using said technologies from C, writing everything by hand. Using ActiveX, nowadays COM/UWP, is never an issue from Delphi, C++ Builder, .NET, Visual C++ via MFC, C++/CX, C++/WinRT, Eiffel.
I once did some Java EE in Eclipse. They both look mostly the same to me. A mountain of crufty crap covered with as much lip stick as it took to make it sort of flop along.
I'm sorry if I'm stepping on toes here, this is just my experience. May I ask what you're using component frameworks for these days? I spent 13 years professionally writing reservation and accounting client/server apps in Delphi but never even came close.