WordPress is, in my opinion, one of the most successful open-source projects for the masses. You can mention many others that are used, including some that power WordPress itself, but no other is used at the scale as WordPress does. From IT professionals to people from all kinds of proficiency levels to people who want to showcase their passion, use WordPress, and for a good reason.
The tool
First, it’s a very mature tool. It was released on May 27, 2003, and it’s constantly being upgraded with security patches and new features. According to the website, and I think this is a staggering number if it’s accurate, “40% of the web uses WordPress, from hobby blogs to the biggest news sites online”.
The problem it solves
The same mission applies from its inception until today. To make blogging and posting content as simple as possible and available to everyone. Going from an idea to a good-looking website is fast. There are thousands of providers that even do the setup for you to focus on the content. There are millions of plugins and themes to choose from and, to me, this is the biggest advantage. Since so many people use it, the plugging ecosystem is healthy. If you want to do something extra that WordPress doesn’t support, you can find a plug-in that does it.
Why I use it?
Although I know how to build a website, I don’t want to spend time doing so. Thinking about hosting, security, design (I have 0 taste when it comes to design), and much more is a waste of time since it’s already done. People are working on each of these tasks so that I can focus on the content. Since it’s so widely used, security patches are frequent, which is a plus for me. My hosting takes care of all the rest. Saving time is essential for me, and WordPress and all the plugins that I use perform a much better job than I would.