Professional software developer here. It’s definitely a career. I do agree it’s like art, it requires you to fit stuff together like a puzzle to get it to work. But I don’t think that makes it less of a “serious” career - there’s a lot of money in the field and as the world gets more and more invested in computing it’s become a very in-demand skill.
I think the joke is that people who don’t know how years work would think 4999 BC was before 5000.