In reply to wlcdesigns.

At first, a couple of years ago, the customizer seemed a bit clumsy implemented, was slow and, most of all, very limited in power. But it worked as a demonstration of how to get instant preview of changes. The feature most absent, after the introduction of widgets management, was menu management. Now (upcoming 4.3), with this, and with partial updates, it feels a lot more mature.

I really look forward to get rid of the big options pages, even if they will not disappear for plugins yet. Future will show if plugin developers will adopt the new API,

With the exception of the new site icon setting, it's possible for plugin authors to disable it without taking away functionality. And it's easy to create an options page for site icons. It's also easy for theme authors to offer a plugin to manage theme settings through an options page, as an alternative to using the customizer.

Both lovers and haters of the customizer should be able to live happily together for years to come.