Ask Slashdot: What's The Best CMS?

Slashdot reader pipingguy recently inherited a 2012 installation of Joomla 1.5.26, and while performing four years worth of updates, began wondering about other content management systems. I've built more than a few static websites (I use Sublime Text 3 or Atom, not some fancy-pants WYSIWYG doohickey) and am quite familiar with CSS, but databases not so much. I've been through lots of online documentation and am a bit bewildered, but I'm following the recommendations regarding backups and the like.

What are Slashdot readers' latest opinions on the three most popular CMSes -- Drupal, Joomla and WordPress? Any tips for me before I accidentally blow away the existing site and have to rebuild everything...?
Leave your educated opinions in the comments...