That's not an inherent property of WYSIWIG. You could equally say that "The problem with building code is that it is hard to automate (and is not composable)",

That's not an inherent property of WYSIWIG. You could equally say that "The problem with building code is that it is hard to automate (and is not composable)", which is true of most programming languages, but then there are IDEs that largely automate tedious programming tasks and there are languages designed for meta-programming; what is lacking is good support from dedicated tools, and a design for automation. I have some ideas of my own on such system could be built, but fortunately many other independent initiatives have emerged lately in that direction (mainly thanks to the ideas by Bret Victor, and all the recent advances in the intersection between Reactive Programming and user interfaces).