Yes it was, your Java 8 code won't compile in Java 9, if using anything that was removed or blocked due to the modules changes, library and runtime are part of the language.
A programming language isn't only grammar and semantics.
The affected APIs were from packages where is is easy to tell from the name that they were not part of the standard.
These can be very useful in certain circumstances, but it should have always been clear that there is a risk they could one day be changed in an incompatible way or removed.
