Having built Wordpress CMS systems in a variety of scenarios I find it an incredibly frustrating piece of technology. For common framework expectations / patterns in 2016 it feels at least 5-10 years behind. It's difficult to migrate, have multiple environments, deploy, and so much more. In almost every respect I find alternatives such as Craft CMS (php/yii) or Wagtail (Python/Django) vastly superior and much easier to customize. The only reason I find it continues its momentum is that it has word of mouth for managers, mindshare with editors / content managers who know the admin ui well and expect more of the same, and it has a very large plugin/theme ecosystem for people who want to get started very quickly. The problem, especially with some of these themes is that they are almost impossible to extend and maintain and they are very bloated. I find that lately I either choose a flat file CMS for a client (Kirby, Grav) or if its a very simple site I use either Squarespace or Webflow and for other cases I choose Craft CMS, Wagtail or others which need a database backend.