The GNOME devs are actively closing the software as much as possible; their software philosophy is probably as closed as you can get while being formally open source.

There are many interesting informations around to get a picture of how they think; this article has interesting concepts:

https://igurublog.wordpress.com/2012/11/05/gnome-et-al-rotti...

and this is the most relevant part:

  I think one of the most important cases against applets (as they are currently defined
  in GNOME) is that they are extremely detrimental to the Identity of the product or 
  platform. [...]
 
  Let’s say that we are trying to define either a product or a product platform. I don’t
  think it is possible to do this without some “brand” coherence. And it is arguably
  impossible to do this effectively with such an ad-hoc/individually-customized design
  identity.