Drupal's core architecture is extremely dated. You might like the hook system, but it is in no way a replacement for dependency injection a la Symfony2.
Yes, by mine. I've spent quite a lot of time elbow-deep in Drupal. It is better code than Wordpress--though that is damning with faint praise--but does not really reach the bar of a Lithium or a Symfony2.
Now, it's certainly more normal-friendly than Symfony2 or the like by way of allowing non-developers to implement (a subset of) features, but I wouldn't call it programmer-friendly and I wouldn't use its internals as an example of good code.
