Back when I was setting this site up for the first time, there was a common theme across many of the resources I was reading. Almost all of them said to treat a personal site as a 'business card for the Web'. While that idea is a fine starting point if you're only looking for a site to show some basic contact information, I think doing so does a disservice to yourself.
A personal site offers a dedicated place to experiment across the entire tech-stack; not a deliverable for a client that is handed over and then never touched by me again. A personal site is a place to try out that new API, see what can be done with CSS, truly discover what the Web can be.
meta tag[^2]. JS is still one I'm somewhat conflicted on, albeit very easy to misuse, when implemented purely as a tool (Read: enhancing functionality) JS is actually a lot of fun. Having a personal site puts you in the position to more freely experiment with these technologies and in doing so not only build a better site (in functionality and/or design) but also become more knowledgeable about your tools in the process.
Of course that's just talking about the underlying technologies. There's also immense benefit in writing a blog as well. Although my earlier content was somewhat more sporadic in focus, I've largely settled into writing about technology now, something I think is for the best. As I've said previously, working in a Computing-Science related field inherently requires the continual learning of new skills. This is something that I feel plays to the strengths of a technical blog. I get to read about new topics to write about, and you (hopefully) get a better article to read as a result.
Writing a blog effectively results in a feedback loop. I discover a new topic, decide to write about it and in the process of doing so I need to research more about the topic to help ensure that the comments and information I present are grounded and factually correct. In the process of researching I'll inevitably discover new topics from which another post might spawn. Repeat that process a couple of times and you've just added immense value to your (and your readers) knowledge base(s).
The Web was established as a means of sharing information and as easy as it may be to simply consume the content available online, getting personally involved by creating new content helps offer a new perspective, a new discovery, a new conversation. It helps keep the Web as a place where the more people get involved, the more value there is to be found.
[^1]: At the time I had a very shallow understanding of JS and most of the views expressed by others I was reading was that JS in almost any capacity was a mistake (E.g Pages taking tens of seconds to load, broken features because a script failed to run etc.)
[^2]: See services/protocols like Webmentions, Opengraph etc.