WordPress is an amazing volunteer project, with real bodies working to keep the Theme and Plugin repositories online, as well as the support forums humming along. With so many users on the web using WordPress, it is a big job.
The Theme Review Team knows they are behind in reviewing new themes, and have a (action!) plan to reduce the queue. There is a revised workflow presented, as well as a plan to develop a theme check plugin on GitHub.
I am very grateful for this work to be done, and I’ve considered joining the theme review team myself. I’ve heard it is a good way to learn decent theme coding standards, and I intend to release a theme to the public repo (eventually, no timeline for that!).
If you are interested in theme development and how the WordPress infrastructure supports it, follow the Theme Review Team make blog. 