C still has it's place. It's not glamorous, but it works. COBOL has no decent replacements. Yet. Some have tried. Almost all have failed. Old does not mean useless. If it works, then it's not wrong.
I guess you need to inform yourself about migration projects that use those products to bring COBOL codebases to modern platforms, where new features are then written in Java/.NET languages, while the old working code is left as is.
.NET, Java are good COBOL replacements.
http://www.fujitsu.com/global/products/software/developer-to...
https://www.microfocus.com/products/visual-cobol/