In reply to KTS915.

Thanks for the feedback. Many of these issues are actively being worked on, and, as always, we're seeking help from more contributors. We currently have only three people spending significant time contributing to the Customizer in core, and we all work on core on a volunteer basis. The best way for the Customizer to improve quickly from a usability perspective is for more people to get involved in contributing. See http://make.wordpress.org/.

I'll also note that many of the issues you note are related to the way themes and plugins implement the Customizer. By design, related options should be in the same section, but only one section is visible at a time to make it easier to navigate to different sections and panels. Think of a section like an admin page - you can't have multiple admin pages open at once either (in a given window). When themes and plugins implement their options in the Customizer, they should make every effort to remove as many potential options as possible, per the WordPress philosophy.

The Customizer does not add bloat in any way; rather, it is designed to reduce bloat. By providing a new, standardized UI API outside of the admin, it offers an opportunity to remove the horrifically bloated settings & options pages that have plagued the admin for years. Also, the way the Customizer uses Ajax, it's actually much more efficient than things in the admin, rather than adding bloat. Menus in the Customizer are a great example of that (see https://core.trac.wordpress.org/ticket/14134).

The reason that the Customizer is being "forced" is because, simply put, it provides a better user experience. It isn't perfect but it's the best option we have right now, and it has a very good API that will allow it to continue improving over time. The future of WordPress administration is on the front-end, with full live-previewing capabilities with the Customizer and eventually front-end editing.