I spent several months trying to port a site to Drupal. And it didn't work. There you go: One great example of where Drupal fails. If you want to build something in Drupal, you gotta do it from scratch, and you gotta do everything the Drupal way. And there's a lot of shit you can't do in Drupal. I have node types on my site that support 100 fields. Do you know how much memory Drupal takes when you load up a CCK form with 100 fields? And how does drupal support multiple languages? Instead of supporting multiple languages per node, you have some hacked up shit where multiple nodes are tied together (At least when I was working with 6). And if you want to edit two languages at once, you have to dig into the heart of the mostly undocumented form engine and load two nodes at once. Which didn't work because it maxed out my PHP install's memory. Why the fuck is Drupal taking several tens of megabytes for only 100 fields?
And then you get to the code structure. It's not object oriented. There are global variables everywhere. The names of variables are completely unintelligible and the depth of data structures is heinous. It's the definition of spaghetti code.
Ok, if you are a CMS jockey and every $3k site you build is pretty much the same with a different skin, then yes, Drupal is great. But if you are an actual developer, and need to do a lot of custom things, then try a real framework like Zend, or Codeigniter, or Laravel, or Yii, or even another CMS, like ModX or TomatoCMS or Pimcore. But for god's sake don't waste your short life by dipping into the cesspool that is Drupal.
I ported my site to Zend in under two weeks. While it's not the least resource intensive framework, it is rationally designed around OO patterns, and the code comes out beautiful and maintainable.
Is that specific enough for you?