Java has Optional as well, but as you well know, you can't just bolt ADTs onto the side of a language and wash your hands of it.

The whole system has to be designed around it to get the benefit of it. Java programmers will be checking for null until the last line of Java is written.

Sure, but the argument was that folks would reject it, when they in fact have explicitly added it. Its effectiveness is another story; not only along the axis you were talking about, but also others, but that's a separate conversation.

The language maintainers adding new features to appeal to people newer to the language is not mutually exclusive with veterans of the language not adopting the new features.

Some form of optional has been in wide use in the c++ community for more than 20 years.

> Java programmers will be checking for null until the last line of Java is written.

Not necessarily. Adding nullability types to Java is a smaller undertaking than adding generics was.