In reply to jawittdesigns.

The customizer itself is actually a really good thing because it standardizes how appearance-related items are handled. This is particularly nice when switching themes and needing to set the new theme up. Client sites are a minority. The vast majority of sites run on publicly-released themes. It makes sense to standardize something for the majority and have a plugin to cater to the minority (i.e., disable the customizer for a client site).