https://old.reddit.com/r/learnprogramming/comments/g5zvpa/ps... - is probably the most succinct from that thread. Your challenge isn't just learning Cobol - that's relatively simple. It's all the surrounding infrastructure that is also very different - different OS, different file system, different database, front-end is 80x24 green and then you get into source control, build and devops which will all be different.