BTW author of article mentions also incidental complexity of Java classes. It's worth consider too and maybe it's more accurate picture of problems with Java (and many other languages, it's more like poor design and "cult of complexity" than technology problems).
There are too many abstractions, classes, interfaces, inheritance, needless design patterns... it kills productivity and maintainability and ability to understand such codebases.
If 90% of that java code was generated, then what exactly were they doing?
Also, there is such a thing as too much abstraction, but there is also such a thing as too little abstraction and refusal to use design pattern where it fits, because "it would be too complicated" alias someone was scared and lazy to learn. Neither is good. The projects I have seen that refused these "advanced" techniques all ended like hard to maintain and makes sense of mess of special exceptions to special situations - hard to reason about code.
Design patterns are not hard and abstract thinking is as useful as good memory. Refusal to learn either is not mark of good developer.
Basically, you read stuff it is generated from, and you dont read generated part unless you suspect bug in generator.
The other occasionally generated stuff is syntactic sugar - hashCode, equals or delegate methods. That is quick to read once you get used to how it looks. More importantly, if that sort of thing is 90% of the code, then there is something wrong.