I really like WordPress for blogging and it is really the best platform out there for doing so. That much said, it has one sticking point with me which is that it is too closely tied to MySQL and MariaDB for the database backend. For those of you whom are not Information Technology professionals, WordPress requires a database to function properly. In an ideal world, we would be able to have a choice of different databases to use but we do not.
I would like to see WordPress start moving towards an abstraction of the database functions to allow us to use MySQL, PostgreSQL, or for the truly lightweight website, SQLite. The licensing and general attitudes of MySQL and its cousin MariaDB leave a lot to be desired. The licensing of PostgreSQL is much friendlier and more open than the MySQL and MariaDB pair. In order to make this happen WordPress would need to adopt the PHP-PDO extensions and use them to communicate with the chosen database engine.
My wish for the WordPress developers is to become less married to a single database and to start a code migration to support PHP-PDO. I hope that this is not asking too much. One thing that WordPress is mostly really good at is extensibility and flexibility. I want to see it continue in this tradition.