It has a very different architecture from what web developers are used to. It has an event driven architecture, somewhat like C. During the process of running t

It has a very different architecture from what web developers are used to. It has an event driven architecture, somewhat like C. During the process of running the code on a HTTP request, there are multiple hooks (actions and filters) that get called, where you can attach your own function in a plugin or theme. About 5 years ago I saw a lot of requests like "When will WordPress move to MVC?", but those questions seem to have died out mostly. Then there is the OOP architecture of data and communication that is loved by a lot of developers. I think Joomla and Drupal have moved into this direction. This makes the code in WordPress look oldfashioned, it is partly still procedural code, with some classes added into it. WordPress community very much wants things to be backwards compatible, and so far that works out.