My question is the same old question, maybe with a twist.
From the complexity of some sites on the web I guess I should also learn CMS.
What should I learn? I won't name names so I don't influence anyone.
I say the main ones are Wordpress, Joomla and drupal depends on the audience and you. Everyone has there own preference, too me Wordpress is more like a normal website were joomla you have modules for sections like header, advert so on... try them all simple CMS is good as well if you want a very basic simple one. Most can produce simple to complex websites.
Yes, Wiordpress seems to be easier to learn than Joomla or drupal. I'm new to cms too, now I'm learning Drupal, because my friends think it's very perspective. I think they are right So my suggestion - learn Drupal!
If you have no CMS experience, I would start with Wordpress because the learning curve is pretty flat imo. Once you get the hang of it and know the fundamentals of how CMSs work, I would move on to Joomla or Drupal. It wouldn't hurt to try you're hand at an e-commerce platform like Magento either.