What to use instead of XMLBeans now that it has been retired?

Have you looked at JAXB? I haven't done anything with either of these, but googling for "alternative to XMLBeans" brings up lots of references to this package. Here's an article that compares them...

http://blog.bdoughan.com/2012/01/how-does-jaxb-compare-to-xmlbeans.html

XMLBeans has been unretired:

The Apache POI project has unretired the XMLBeans codebase and is maintaining it as a sub-project. Until now the XMLBeans codebase was held in the Apache Attic where former Apache projects are kept for the public good.

The latest release as of August 2020 is:

3.1.0 (March 26, 2019)

Having said that, I am not sure I would recommend using it, based on its history of retirement. Other solutions, such as JAXB, might be prefered since it will probably be better maintained in the future.