I'm not sure the problem is necessarily Drupal, but I tend to agree with the post's authors that a Drupal written in something other than PHP would be a nice thing to have. Specifically Python would be really nice.
Why? Look, I hate PHP as much as the next passionate software developer. I did PHP full-time from 2000-2005 until I couldn't take it anymore. I spent a fair amount of time with Drupal and it was technically very impressive even though ultimately it was not for me because the tradeoffs were not where I wanted to be as a developer.
The thing is, what a CMS does is cater to a site which does not have the budget for custom software. A system like Drupal gives a tremendous amount of bang for the buck, and of the open source CMSes, it's hook system is definitely the most powerful once you really understand how to drive it. In the end you're hitting the Drupal sweet spot when you write just a bit of glue code here and there to tune the functionality of existing modules to what you need.
In short Drupal and other CMSes let you build sites with a scope of functionality which would be impossible to do custom development for. In this type of market cost is such a factor that anything less ubiquitous than PHP would be a strike against the system. Furthermore, as the number of modules grow, you need a very large community to keep everything working smoothly, so you don't want to go with a language that has lesser adoption.
Personally I can't stand CMSes because I feel like the abstraction is at the wrong level. To me it's mediocrity by 1000 tiny assumption mismatches. Using Rails or Django I feel like I can craft a minimal, excellent and highly tuned UX exactly to my vision with a better language and lower overhead. Making a CMS in Ruby or Python doesn't address the root pain of living within a heavy and immobile scaffolding. There's a reason you don't hear much about the many open-source Rails CMSes that have been floated over the years.
I don't know about Drupal - I would tend to agree it's a little too cumbersome to the point where I would rather write something with a good framework like Django.
But WordPress is really nice, aside from PHP, and my once-off design-a-simple-website projects that use it would be a lot simpler if there were something similar that had a better language. PHP does add a significant amount of gymnastics that make plugin development more difficult.
I don't mind living with a heavy and immobile scaffolding for small projects - but using bubblegum, shoestring, and when necessary sauter to put what little additions I need on is a lot more annoying than just having a clean, standard set of screws and brackets. WordPress especially has a decent set of screws and brackets, but at the end of the day it is PHP and I see a lot of stuff that looks suspiciously like bubblegum.
As for Drupal, I'm not saying I have an incredible amount of experience in it, but taking it for granted that it's a useful framework, I imagine it would be more useful if written in Python or Ruby. Also, I don't buy the argument that PHP is easier to find - I think you would actually have to go out of your way these days to find a place that had PHP but not Python or Ruby available. Certainly all the cut-rate behemoths like HostGator support it.
The problem you see with these applications is that they are bad PHP, not that they are PHP.
If you would, go take a peek at the Symfony2 framework. It's positively brilliant code, and it's PHP--Fabian Potencier and friends are excellent programmers, and they write excellent code in PHP.
I'm currently in the process of building a migration path from our two different older PHP frameworks (MidCOM and Midgard MVC) to Symfony2, and I've really been impressed by the community.
They seem to be very receptive to new ideas, and passionate about code review. I've received lots of GitHub comments on my bundles even though the commenters probably would never actually use them.
And when I found an issue in Symfony2 itself that made integration with AppServer-in-PHP harder, Fabien fixed it within the hour of getting reported.
