No really, in fact I'd say the opposite.

The issue with COBOL is any old idiot can't write it. If someone is touching the COBOL they are going in and making minor changes/expansions to an application that is older than the average HN user and those changes and expectations are well defined.

With Java and/or language of the day your cheapest run of the mill contractor given exceptionally poor instructions will crank out X LOC per day where X is the required output for them to keep their job. Maintaining that code will be some other bastards problem.

Heirloom Computing, I am CTO, have transpilers for cobol and pl/1. code transpilation is the easy part. Create a Grammer for the source language, generate the ast, transform the ast to the target language ast and generate the code. Now make that generated code run and behave the same way as on the mainframe and give it all the subsystems that exist on the mainframe for transaction, file handling, security etc. This is the part that is difficult. Fortunately it's already solved and in production with our clients.

So transpilers do work and are in production but our biggest competitor is inertia.