I’m a fan of WordPress, but there are definitely issues that impede coders trying to work with it. As a small example, there’s get_the_content() (returns) and the_content() (prints), but there’s get_permalink() and the_permalink(). Then, there’s just the_date(), because it accepts an argument indicating whether you want it to print or return. This kind of thing drives even an experienced WP person up the wall, because you’ve always got to be Googling the usage – and it speaks to a deeper lack of attention to detail in the code.
Another glaring issue is the lack of built-in caching. It even used to have it, but they ripped it out and never replaced it. You shouldn’t need a third-party plugin to have basic caching in a system like WordPress, particularly with all the other bells and whistles it builds in.
To paraphrase (supposedly) Churchill, though, “WordPress is the worst blogging system… except for all the others”.