Is anyone going to mention that the Customizer frequently doesn't display correctly? Now we have good options - plugins or child themes. We'll lose those in favor of a solution that will confuse people and not work as well.

I use the plugins on most sites and have bits of CSS that are not theme-specific. Other tweaks will be theme related. I can comment those out when I want to change themes but am not ready to lose those theme-specific changes just yet.

I understand WP.com wants to compete with Squarespace and the like . . . but so much more important work could be happening for small business website builders.