> I can do it single handedly

For every 1 programmer working on a Cobol system who would and could rewrite it, there's another 3 who actively resist rewrites to keep their jobs and put bugs in the system to generate overtime-paying after-hours callouts. There's yet another 6 programmers who don't have the aptitude to program but who somehow managed to get into their job and are just productive enough to avoid being terminated. And perhaps they bring one of their kids to work for the day every now and then.

You don't get to do a Cobol rewrite single-handedly when there's 9 others on the team working against it happening.