As someone who enjoys playing around with MVS on an emulator just to get an idea of how the IBM mainframe stuff actually works, I can understand the pain of job control cards.

I heard someone mention that only a single JCL statement has ever been written. All others are copy-pasted from another one and just modified.

I believe this is true, since I had to try a lot of times just to be able to change JCL script to read FORTRAN code from a separate dataset.