As a Drupal developer myself, I'm not really sure why Greg had to mess with 1000+ lines of Garland-adapted code specifically because he goes on to say that he could do the same thing using Zen in under an hour which means his customization needs weren't too detailed to even require messing with 1000+ lines of code. I'm sure he knows what he is doing, but in my own experience I've managed to use the php-template engine with CSS to create some fairly customized sites in very little time without requiring Zen or any other 'specialized' base theme or requiring messing around with copious amounts of php code.
As for multimedia and no "native" support for images, while I am not familiar with Joomla or other CMS systems to make a fair comparison, Drupal does have many third party, well recognized and documented modules for this very specific purpose that integrate very well with the base system. The "installation" process is standardized and the extended help system delivers useful information to aid the developer. I'm assuming the reason that multimedia modules aren't integrated with the base system is because it allows users to consider options to implement galleries, videos, etc within the Drupal system and allows innovation (more options for end-users) and regular module updates without requiring multiple Drupal releases.
In that sense I would compare Drupal to C. A core system with a very small footprint with the bulk of the functionality being relegated to library code (modules in Drupal speak). I guess, as and when a module becomes the standard way of doing things in Drupal, it will get integrated into the core (like the standard library in C). The CCK module is a very good example of this which is being integrated partially into the core in Drupal 7. Personally I found CCK, Image, Views and Panels (all Drupal modules) invaluable to all my projects and they have become part of my "standard library" of sorts. For needs not satisfied with these modules, I just Google Drupal + need and choose between the numerous modules that come up.
Having said that, I do agree, Drupal could do well with "pre-installed" modules for basic functionality like image uploads and video integration with the option of overriding these with third party modules to perhaps make things a bit simpler for the uninitiated. But for me, the current state of things isn't a deal breaker given that I have my standard modules stashed away and I just have to copy to my new Drupal installation to have a very usable base system.
Like all else, Drupal (like C) has a very specific philosophy and if that gels with your preferred development methodology, then great! If not, the alternatives are good too.