open source projects don't need snazzy websites that look cool. They need plain minimal sites without ads that are quick to the point.
free software says: "we are so cool that we don't need to win you over like a business. Here's the facts. Make up your own mind"
It's also that they usually cannot afford professional web designers, and are mostly ran by programmers, not designers.
Being elitist about free software as an excuse is a pretty shitty excuse. Web pages are there to inform, web page design is there to make the information welcoming and available to everyone. Businesses know this and design their sites accordingly, however they have incentives to also hide information from sight to influence your opinion. Bitcoin not having that incentive doesn't mean it doesn't have the incentive of attracting new users/demographics.
Currently the demographic for are those who have varying economic/politic opinions from the masses -or at least are more educated about what they believe in-, and tech nerds who like open source stuff and find bitcoin interesting. With the increased use of Bitcoin and more acceptance, it is already attracting a broader audience due to more vendors accepting it thus making it more viable. With a site with mostly words, most of the new users could be scared away. That drupal theme is more compatible with including small diagrams while with the other example it would seem out of place due to the boring and sterile feeling the design gives off.
However you're probably not trying to be elitist about it at all and just confusing minimalistic design with lack of forethought on design. The drupal theme is indeed minimalistic, and with some corrections, could be called plain as well.
The other design could be worked to fit the bill. The area above the menu is too big with the huge logo. The menu itself doesn't tell me what page I am on. Making the logo smaller and incorporating half of it on the menu bar would reduce the wasted space on the top. Moving the logo to the left and having the menu align on the right would make it more attractive. The menu itself could remain black with a small space of white above it for the BITCOIN part of the logo while the menu bar itself has "A P2P VIRTUAL CURRENCY" and the bottom part of the logo in the menu bar itself. (if you want to be clever, you could make it a bitcoin going into a coinslot). The example needs to be widened to see how it would look on normal monitors. However you don't want it too wide, you would have to center the information, but if you center it, you would need some sort of side-content to distract the eye away from all the empty space. A bunch more stuff would be needed for all that to look smooth and as welcoming as the drupal design.
What if you turn the blue in the middle into pixel art as a homage to the original bitcoin.org design ?
Pfft. It's just more work.
I am unsure if you're trying to be ironic in criticizing the page design itself, or being totally honest with the idea of turning the download area into the current bitcoin blue pixelation.
Personally I think the idea would make the download area too busy.