And it's not cause I don't want nonprofessionals to build sites, but because when I *do* want them to, it's possible with this. Too many CMSs get too complicated. Last Joomla site I built, I wrote a 50 page manual for and conducted a 6 hour training. And I don't think they're updating their own site even now. It would have been easier to teach them Dreamweaver.
IMO, CMSMS is a lot easier for me to let a customer edit their own site, you got Tiny, you got a simple menu system (and can write all the menus you need from one hierarchy) and they can manage that.
Not to rag on Joomla, but it's the one I spent the most time on before this. Who the heck is it for, other than the Joomla community?
I bought my first template and edited it cause it was too hard to figure out. Managed to make my second one, but... still... wasn't particularly easy. Modules are easy to write, but to do anything actually active, you have to write components, and hence delve into the world of all the Joomla-specific code... to just do simple things like have a form write to the database requires a certain amount of standing on your head. By the time we'd built a medium-sized project with it, hubby and I utterly hated the thing for making us jump through so many hoops.
We eventually figured it was simpler to write standalone php programs and just make them look like they were in Joomla rather than try to actually write for Joomla.
And it's actually more time-consuming to find a prebuilt extension and load it than to write your own. They're all so complex that to find the one that does the one bit you want to do can mean installing and demoing scores of the things, and for each one you register on the author's site, read his/her forums to figure out if it's junk or not, etc. I've lost entire days of my life to trying to find an extension.
And as noted, Joomla is NOT for non-technical end users to manage their own sites cause the interface is so convoluted and confusing. I mean, to just let them edit with Tiny in the front is OK, but as soon as someone has to get into the admin interface to be able to add pages or something, you're looking at producing a training manual and conducting a training and they're still bewildered. Not cause it's *that* hard, but it is complex, and most of my customers don't update their sites daily, so don't really learn it.
I don't know about Drupal, I just know I chose Joomla cause it was supposed to be the more user-friendly. I shudder to imagine what Drupal is like if Joomla is the easier.
IME, to be a Joomla developer means... being a Joomla developer. That itself is a full-time thing and it kinda hurts your brain after a while cause so much of it is so convoluted.
I dunno, after a few projects, I decided I didn't want to be a Joomla person. It didn't work better for me than writing everything, including a backend content manager, from scratch.
Wordpress is a lot easier, and you can bend it around to make it a web site rather than a blog, but the backend is still more complex than most of my customers need to be exposed to, at least partially cause it's really not a CMS.
I looked at a LOT of CMSs this past month. And I really have not seen anything like the admin in CMSMS which is so obvious and easy to figure out.
IMO, the "made simple" bit is more important than the "for professionals" bit. I know I can explain this to my customers.
(I have to admit, I don't like Smarty yet though.)
To get a bit more on topic, I don't understand themes. I mean, I've seen some lovely ones, all the way from plain XHTML themes all the way to the many CMS themes, including some very nice CMSMS ones.
And I've seen some in every darned system where it's quite obvious a geek thought he was an artist but was mistaken.

So there's some nice themes and some made-by-people-like-me-who-ought-to-know-better themes. But in either case, to make a theme "yours" in any way, you have to edit all the artwork, at least make a new header, change the colors to match, etc.
So... it's not like having a fully made theme is much of an advantage over having a basic layout and stylesheet. You still need an artist if you don't have those skills yourself, and you sitll have to edit up the stylesheet to match the art.
What I don't get is... do people really want unedited themes? A web site that looks exactly like another web site?
Do you guys have customers without logos, without corporate color standards, that let you just put anything up there? Cause... I've just never had anyone want me to build them a site that looked exactly like another site. Even when building sites for different branches of a national nonprofit with specific rules for colors, logos and fonts for the whole country, the branches didn't want their sites to look the same as each other.
Themes as demos make sense, especially for artists. And themes as a starting point to roll-your-own make sense, but... just themes themselves to install and use don't make sense to me.
Not for real sites, for someone wanting to blog about their hobby, OK, but... not a real site.