While learning new tools and frameworks (Azure, for example) is necessary if I want to actually deliver any software, in more recent years I'm much more interested in the practices and patterns that make code testable, maintainable, and decoupled from concrete implementation details.
One of my favorite books, Code Complete 2nd Edition, has been around since 2004. I wish I'd known. If you haven't read it, read it. Give a copy to a new programmer. You'll make the world a marginally better place.
If we can't explain something then we don't understand it. So I write blog posts to see how well I understand what I'm learning and to share with others. I used to send my coworkers long emails when I found something interesting, but that's not a great way to communicate. People don't like long emails and they just disappear into the ever-scrolling inbox (or worse.) I'd also like to think that writing from that perspective makes it more accessible to less experienced developers who need really simple examples.