Machine learning. I used to think it wasn't worth learning but I was recently convinced otherwise. ML is one of the few skills that can enable an individual to make a 10x change to a business.
What convinced you? I'm also in the skeptical bracket.
Someone at my company drove a 10% increase in revenue by coming up with a new way to apply a model. There is nothing I can do short of creating a new product in my free time (which at that point I should be doing that for myself) that could drive that kind of revenue increase.