There are plugins and you can extend with modules written in c++. Are you referring to another type of extension?
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You can include c++ modules and use them like another class.
http://docs.godotengine.org/en/3.0/development/cpp/custom_modules_in_cpp.html
I don't completely agree with that assessment, I've used some that are coded correctly. Could you point to the ones you're talking about with the 27 pages or are coded wrong? I also think Godot is easy to use software for a programmer, at least it was for me coming from GameMaker and Unity. As far as building a game without coding, Godot has visual scripting. I have zero experience using visual scripting with Godot, but in my opinion you won't be able to make a game of a certain quality without diving into some form of coding anyway.