I have used CMSs (Content Management Systems) for years, mainly Joomla, but also others. I don’t consider WordPress a CMS, but that’s just me. Anyhow, I came across a new (to me, anyway) one a few weeks ago that has very quickly become my favourite.
It is called ProcessWire, and it is unusual because it has no front end. (The download comes with an example front end, but there is no requirement to use it.) So we PHP and CSS dabblers can have a field day! All the ProcessWire CMS (or content management framework) does is look after the back end organisation of fields into pages and pages into a hierarchy. It does a great deal more than that but click the link and read more there.
Every time I use ProcessWire I find new delights, whether in the way it makes data available for front end display or in the control it gives of data in the back end, and the community, though quite small, is knowledgeable, friendly and helpful. I could go on at great length, but get over there and find out for yourself!