Many of the complaints here are common to all major web CMSs, which is what drove me to write about "Decoupling Content Management" two years ago: http://bergie.iki.fi/blog/decoupling_content_management/

Since then, there have been common infrastructure components like Create.js, PHPCR, and Symfony2 that have been widely accepted by many of the projects. Through that, the state of Content Management is now steadily improving.

Sadly, WordPress has so far stayed outside of this development.