This one kind of nails it. For me it’s very hard to believe in ”gallery of Plone themes”. Theming Plone is easy, but building a complete generic ”not buggy” Plone theme is hard. Affordable Plone theme is usually limited to support only some limited use cases.
What we could maybe do, is to ship a bunch of pre-customized Barceloneta themes. Like with a dozen different color palettes. And maybe we could have a version of Barceloneta with real CSS variables to allow easy customization without ”building less” (Can I use... Support tables for HTML5, CSS3, etc).