If you are already a developer and you want to improve your CV to get into more crypto related jobs, it definitely worths it. However if you are not a developer, learning courses about blockchain will not help you aside from maybe having a deeper understanding of how blockchain works, or maybe you can write a white paper if needed be but thats about it. Without any financial gain from it, I feel like a "course" is always useless, its everything you can find online yourself, course just compacts it and sells it to you, nothing else.