I’m just jumping in here, from a different perspective.
I am a senior programmer, what 30 years now? Man. I was working on an indy Multiplayer game and used 3 different engines over the years. Irrlicht, Ogre and C4. The C4 engine was the most promising one because it had an editor and stuff. But it quickly turned into a nightmare because the editor was unusable, the import pipeline was broken, and getting assets into it was a gamble. I ended up writing my own converters using 3DS as my level and object editor. It was bad, believe me.
Unreal helps a great deal with the art pipeline and the organization of assets. I agree that it would be nice to have a setup where my program provides the EXE and UNreal is a library that I call. That’s how it should be when you write a program in C++ . I also agree that there must be more tutorial material and documentation to make the C++ interface usable for anybody who does not want to spend a year fulltime studying source code. I don’t study source code. The C4 engine had hardly any documentation and whenever you asked a question the answer was “read the sourcecode”. I don’t do that. I use only software that is documented because my time is too valuable to read source code. Probably comes with age.
So Blueprint is a godsend for me. I can make the client in Blueprint, the right click/intellisense thingy helps me to figure out things I dont know anything about, because I often just type some guess words and then get a list of fitting things that allow me then to research them and find out what I need. I sue C++ more like an under-the-hud thing to interface to the network library I use but otherwise stay away from it. I would use it more if I could, but like I sad, lack of documentation is a gamebraker for me.
If I could make a whish, I would make it so that the editor can be used for the whole import part and organizing assets and that there was a second form of Unreal that can be linked as a DLL or so. And of course documentation.