Writing my blog (https://thehousecarpenter.wordpress.com/) has helped me learn things because it provides me with a concrete motivation: instead of having the rather vague and amorphous goal of "learn about X", I can think of my goal as "learn enough about X to write a blog post about it". That's always been the idea behind having the blog, and it's worked decently for that purpose. It hasn't helped me at all with my career or with connecting with people, but that's unsurprising as I've never cared to optimize for those goals.