Write for humans. It is really simple as that.
Think about it. Humans build the computers and the programs for the search engines. Humans search online and read. The search engines do pick up what you write about, but it is not the search engine that you must rely on alone to receive traffic.
Writing is not easy. It is not something that comes naturally to everyone and does take some time to learn how to develop your blog voice while also thinking about how to optimize your article so it is crawled well. However, you also have to remember that you need to write in order for your audience to comprehend your blog post, engage with you on that article, and maybe even do what it is that you want them to do. That might be buying a product, subscribing to your email newsletter, or following you on a social network.
It is understandable that you want to make sure that your blog ranks well, but do not forget who you are writing for in the end. Search engine optimization is not as hard as people think it is. If you have a well designed theme that is slick on load time, you only have to worry about the content you place on your website. Regardless if you are writing all of the content on your blog yourself or paying someone, write for humans!