There are so many contributed modules that can help build things out, but I always need some type of customizations requiring (usually a few) custom modules per project. It all depends... I did one project that had dozens of crazy features that we broke out into 70+ custom modules...
But yea, I would say the sweet spot is a customer who needs a pretty large site with a lot of functionality. My 2 cents anyway.
This is in part due to the relative complexity of setup. You do not get your grandma performing a one click install of Drupal and then spending $40 on a theme and buying an extension or two from a marketplace.
The focus on earning money with Drupal really seems to be in being a good developer and knowing how to use the thousands of opensource tools that are available to Drupal. You do not see people cranking out apps or modules for drupal and selling them in a marketplace. This really sets it apart from it's php cousins Magento and Wordpress.
You can literally build anything in Drupal, although I'm not sure you should...
In a Drupal custom module you can do or change literally anything, and you can write whatever architecture you like for your individual component. You just have to integrate with the Symfony2 router and dependency injection container. Pretty cool stuff.
This looks interesting indeed.
May I ask what is your preferred way to learn Drupal for a total newcomer, albeit a truly seasoned developer?
It's a paid monthly service, but well worth the educational value you get out of it (for a few months at least).
Good luck!
It replaced a commercial solution bringing more clarity (but that was also thanks to stricter rules in place defining types of docs, fields etc..), better graphic appeal (but just because the previous one was really crap) and also great search experience thanks to Apache Solr.
As I am a sysadmin, not a developer, I used all built-in modules except one that I modified in order to integrate the authentication with another business system via webservices (only code I developed). As I am also not a graphic, I worked with an external one (that prepared design in PSP so it was a bit a pain to convert it to template)
At that time (2009 I think) I reviewed few other options (WP, ezPublish, plone) but I chose Drupal because the authorisation system with roles etc.. was much more powerful than WP one.
Legos - Custom built web app
Duplos - Drupal, fully customized with some coding
Pre-Built Toy - SquareSpace, Wix, even Wordpress to a certain extent
It's a nice middle ground when you need something more custom than Wordpress and others can provide, but don't want to build everything from scratch.