When a prominent developer and contributor lashes out that Drupal is in dire straits, you better listen. You ought to read his critique of how Drupal core development is stalling, or at least stuck in the mud. That can't be good news for anyone looking to upgrade to Drupal 7. My thoughts after the quote.
In addition to the half-baked, single-purpose product features mentioned above, Drupal core still carries around very old cruft from earlier days, which no one cares for. All of these features are not core functionality of a flexible, modular, and extensible system Drupal pretends to be. They are poor and inflexible product features being based on APIs and concepts that Drupal core allowed for, five and more years ago.
Where would Drupal be if they had worked more closely with the PHP community early on? I have no idea, but a lot of PHP programmers have looked down on Drupal because most of the codebase can be messy, with poor API design decisions, overuse of globals, and leaky separation of concerns. Along with Drupal eschewing Object Oriented Programming and resulting best practices, its no wonder that talented developers would choose to use a framework like Zend, Symfony, or Cake to build a complicated website. It sounds like a lot of short cuts and idiosyncrasies are now baked deep into Drupal core, and ripping them out too much work for core developers.
I've always thought that Drupal's greatest strength is certainly not the great design of its codebase, but the Drupal community and ecosystem. A contrib module usally exists for many common website needs, like managing redirects, creating useful URLs for content, integrating with analytics, and plugging in 3rd party commenting systems. On top of that, there are super-modules like Views, Panels, and Context, which let you prototype and build parts of a website without having to write any code at all. The Drupal community has solved a lot of problems through determination and individual brilliance, but that model can't be sustainable in the long run.
Is there a solution?
Drupal core should cater to programmer's needs, via coherent APIs and pluggable subsytems. A complete rewrite of core, or even big parts of core, would be a waste of time. Drupal would stagnate while other frameworks kept improving. I think Drupal 8 should seriously consider using a framework like Symfony2 as the foundation for core. I mention Symfony because it has an EventDispatcher component that can replace most of Drupal's magical hooks system. The next release of the Zend Framework will have a similar component. A tested framework, used not just by content management applications would expose developers to a wider range of best practices, particularly around configuration management, deploytment, and unit testing.
Contrib should cater to site builders needs and focus on adding features on top of core that they want. Modules in contrib can improve faster to meet user needs, fix bugs, and innovate. This is an idea proposed in the discussion linked above. Moving as many modules as possible out of core also makes Drupal leaner.