Are you talking about the API docs[0]? Or about some official tutorial page for Java the language [1]?
The Java tutorials are seriously out of date (they even mention explicitly that they were written for Java 8, and that they may refer features that are no longer available).
However the Javadoc is well maintained and quite useful, discoverable and thorough in my experience. Certainly one of the best native library docs that I've seen.
I got -2 points for stating the very noticeably obvious. That pretty much sums up just how rusty and old Java has become over the years.
So what is the way to learn Java in 2021? Buy 2 - 3 Paperback books?
These days even Perl has documentation on a site that belongs to 2021. These are some things that you need to do to make your language accessible to people wanting to start new projects.
As of now the only real way to read something about Java on the internet is adhoc answers on StackOverflow.
In fact its more like non existent.
I'd like to think that's a non starter for some one new starting a project in Java.