I feel like the biggest problem is most COBOL code is heavily tied to the mainframe it's running on [1]. There are already ways of compiling COBOL code with a modern compiler [2].
There are also multiple other translation projects:
I doubt it will improve the maintainability. Many of those old programs were written to fit the IBM environment. Besides there was always a shortage of space and memory that forced you to use certain programming techniques that would be totally useless in java.
I would love to see it convert a Cobol/CICS program into a java program with a gui ;)
There are also multiple other translation projects:
https://dockyard.com/blog/2021/08/10/what-if-coboltoelixir
https://www.microfocus.com/en-us/products/visual-cobol/overv...
[1] https://www.ibm.com/docs/en/zos-basic-skills?topic=zos-cobol... [2] https://gnucobol.sourceforge.io/