In reply to Webmasta.

The Customizer is not new, it's two and a half years old. And it's arguably much simpler and easier to use than equivalent features in the admin. If you try the Menu Customizer plugin, I think you'll find that it's actually much easier to manage menus in the Customizer than the admin, especially with many, large menus. That's not simply because there's less space for UI but because the UI is more efficient. And, you can see what impact your changes have on your site as you make them.

When used properly, the Customizer can actually be much more useful for CMS-style sites than simple blogs.