You’ve been programming for forever so for that reason Java and C++ might seem extremely similar, because they are. I commonly accidently write code in C++ while doing java or visa versa. Java if learned completely gives you all the knowledge you need to easily learn C++; however, for someone who doesn’t really understand memory and has always just depended on Java’s abstraction on the subject, getting that abstraction removed is a large shock and can force them to learn a lot.
I do agree though that after you learn the basics of C++, then using either C++ or Java just becomes mainly a preference thing. Though sometimes you can always go back to C to learn things you do in Java more thoroughly (like networking for example). Kinda like LWJGL and libGDX just not as different.
IMHO, people who have started in Java (and did not learn it from a CE type of perspective) should some time to learn the basics of C and spend some time to learn the basics of (as Matheus mentioned) lisp.